The first project i made without knowing anyone who is doing a Deyha cosplay but i really like her design and already made the hanger-part as a practice piece. It has some space on the backside to cram in LEDs, switches and small batteries (e.g. CR2032). The collar comes in 2 versions, one clip-in fully 3d-printed and one to be attached to a band. The download also includes a quickstart guide on how to put it together.

BOM:-fishing line (or similar)-adhesive -electronics (optional)-a band to fix the collar to your neck (optional)