I have heard of people making a mold of a part in clay and using Acraglas bedding to fill in the missing or damaged part. Plus the Brownell kit I believe has brown and black dye with it . Don’t forget to use a release agent .
Make a cast of the piece with the clay in place , then remove the clay piece and cast the grip and use Acraglas to fill in the missing piece in the mold. If that makes any sense .
Seems like a lot of work and time involved but if it’s for your own use it could be a learning experience .
Don’t remember for sure but it could of been in one of Brownell’s kinks book.