Following up on Drac's post, you might find some buffalo bone blanks made for replacing the grips on pistols- not as big a piece as he shows, but probably 1.5" across or so. It should be correspondingly less expensive. Check out your next gun show, or online suppliers.

I do want to vote again for a laser-cut badge- it doesn't get you the craftsman's touch, but it remains affordable - and is precise. Of course, it will never match a hand carved piece, either of bone or some other natural material...