Useful tool for merging armatures in Unity and adding accessories in VRChat. All you have to do is import this and then attach the script to the accessory that you want to attach to your VR Chat character. Drag the game object with the VRChat Avatar Descriptor into the corresponding field and then choose a menu (this step is optional if you want accessories to be permanently on). Once you've done that, just hit "Apply" and you should be good to go! If you aren't, just check the console for errors. If they don't provide instructions on what went wrong, feel free to report it here.
For more information on how to use the script, you can check out this Youtube video: https://www.youtube.com/watch?v=d1GgVg75NGA