Created using https://thunderstore.io/package/Brynzananas/Body_Model_Additions_API/

All code as an example:

using System.Security.Permissions;
using System.Security;
using static BodyModelAdditionsAPI.Main;
using UnityEngine;
using RoR2;
using UnityEngine.AddressableAssets;
[assembly: SecurityPermission(SecurityAction.RequestMinimum, SkipVerification = true)]
[assembly: HG.Reflection.SearchableAttribute.OptIn]
[assembly: HG.Reflection.SearchableAttribute.OptInAttribute]
[module: UnverifiableCode]
#pragma warning disable CS0618
#pragma warning restore CS0618
namespace FreakyEyes
{
    [BepInPlugin(ModGuid, ModName, ModVer)]
    [BepInDependency("com.brynzananas.bodymodeladditionsapi")]
    [System.Serializable]
    public class Main : BaseUnityPlugin
    {
        public const string ModGuid = "com.brynzananas.freakyeyes";
        public const string ModName = "Freaky Eyes";
        public const string ModVer = "1.2.0";
        public static AssetBundle assetBundle;
        public static PluginInfo PInfo { get; private set; }
        public void Awake()
        {
            PInfo = Info;
            assetBundle = AssetBundle.LoadFromFile(System.IO.Path.Combine(System.IO.Path.GetDirectoryName(PInfo.Location), "assetbundles", "freakyeye"));
            foreach (Material material in assetBundle.LoadAllAssets<Material>())
            {
                if (!material.shader.name.StartsWith("StubbedRoR2"))
                {
                    continue;
                }
                string shaderName = material.shader.name.Replace("StubbedRoR2", "RoR2") + ".shader";
                Shader replacementShader = Addressables.LoadAssetAsync<Shader>(shaderName).WaitForCompletion();
                if (replacementShader)
                {
                    material.shader = replacementShader;
                }
            }

            new ModelPart("FlyingVerminBody", assetBundle.LoadAsset<GameObject>("Assets/CosmeticsMod/googlyeye.prefab"), "Body", inputCodeAfterApplying: PlaceIt);
            void PlaceIt(GameObject modelObject, ChildLocator childLocator, CharacterModel characterModel, ActivePartsComponent activePartsComponent)
            {
                modelObject.transform.localPosition = new Vector3(-0.45f, 0.641f, .89f);
                modelObject.transform.localScale = new Vector3(0.3f, 0.3f, 0.3f);
            }
            new ModelPart("FlyingVerminBody", assetBundle.LoadAsset<GameObject>("Assets/CosmeticsMod/googlyeye.prefab"), "Body", inputCodeAfterApplying: PlaceIt2);
            void PlaceIt2(GameObject modelObject, ChildLocator childLocator, CharacterModel characterModel, ActivePartsComponent activePartsComponent)
            {
                modelObject.transform.localPosition = new Vector3(0.45f, 0.641f, .89f);
                modelObject.transform.localScale = new Vector3(0.3f, 0.3f, 0.3f);
            }
            new ModelPart("VerminBody", assetBundle.LoadAsset<GameObject>("Assets/CosmeticsMod/googlyeye.prefab"), "Head", inputCodeAfterApplying: PlaceIt3);
            void PlaceIt3(GameObject modelObject, ChildLocator childLocator, CharacterModel characterModel, ActivePartsComponent activePartsComponent)
            {
                modelObject.transform.localPosition = new Vector3(-0.312f, 0.999f, -0.308f);
                modelObject.transform.localEulerAngles = new Vector3(-127.928f, 0, 0);
                modelObject.transform.localScale = new Vector3(0.2f, 0.2f, 0.2f);
            }
            new ModelPart("VerminBody", assetBundle.LoadAsset<GameObject>("Assets/CosmeticsMod/googlyeye.prefab"), "Head", inputCodeAfterApplying: PlaceIt4);
            void PlaceIt4(GameObject modelObject, ChildLocator childLocator, CharacterModel characterModel, ActivePartsComponent activePartsComponent)
            {
                modelObject.transform.localPosition = new Vector3(0.312f, 0.999f, -0.308f);
                modelObject.transform.localEulerAngles = new Vector3(-127.928f, 0, 0);
                modelObject.transform.localScale = new Vector3(0.2f, 0.2f, 0.2f);
            }
            new ModelPart("LemurianBody", assetBundle.LoadAsset<GameObject>("Assets/CosmeticsMod/googlyeye.prefab"), "Head", inputCodeAfterApplying: PlaceIt5);
            void PlaceIt5(GameObject modelObject, ChildLocator childLocator, CharacterModel characterModel, ActivePartsComponent activePartsComponent)
            {
                modelObject.transform.localPosition = new Vector3(1.47f, 1.86f, -0.33f);
                modelObject.transform.localEulerAngles = new Vector3(-70f, 90, 0);
                modelObject.transform.localScale = new Vector3(0.6f, 0.6f, 0.6f);
            }
            new ModelPart("LemurianBody", assetBundle.LoadAsset<GameObject>("Assets/CosmeticsMod/googlyeye.prefab"), "Head", inputCodeAfterApplying: PlaceIt6);
            void PlaceIt6(GameObject modelObject, ChildLocator childLocator, CharacterModel characterModel, ActivePartsComponent activePartsComponent)
            {
                modelObject.transform.localPosition = new Vector3(-1.47f, 1.86f, -0.33f);
                modelObject.transform.localEulerAngles = new Vector3(250f, 90, 0);
                modelObject.transform.localScale = new Vector3(0.6f, 0.6f, 0.6f);
            }
            new ModelPart("LemurianBruiserBody", assetBundle.LoadAsset<GameObject>("Assets/CosmeticsMod/googlyeye.prefab"), "Head", inputCodeAfterApplying: PlaceIt7);
            void PlaceIt7(GameObject modelObject, ChildLocator childLocator, CharacterModel characterModel, ActivePartsComponent activePartsComponent)
            {
                modelObject.transform.localPosition = new Vector3(1.7f, 2f, -0.2f);
                modelObject.transform.localEulerAngles = new Vector3(-75f, 90, 0);
                modelObject.transform.localScale = new Vector3(0.7f, 0.7f, 0.7f);
            }
            new ModelPart("LemurianBruiserBody", assetBundle.LoadAsset<GameObject>("Assets/CosmeticsMod/googlyeye.prefab"), "Head", inputCodeAfterApplying: PlaceIt8);
            void PlaceIt8(GameObject modelObject, ChildLocator childLocator, CharacterModel characterModel, ActivePartsComponent activePartsComponent)
            {
                modelObject.transform.localPosition = new Vector3(-1.7f, 2f, -0.2f);
                modelObject.transform.localEulerAngles = new Vector3(255f, 90, 0);
                modelObject.transform.localScale = new Vector3(0.7f, 0.7f, 0.7f);
            }
        }

        
    }
}

1.3.1

• Added a nullcheck to prevent log spam

• Added configs for enabling/disabling eyes for individual body

1.3.0

• Updated to use newer API method

• Freaky eyes now look at their targets

1.2.0

• Added API dependency string

• Added eyes to Lemurian and Elder Lemurian

1.1.0

• Updated to the new API version

• Added eyes to Blind Vermin