Steve,
If Bossdog doesn't have it? Try these folks, http://www.angus-campbell.com This is one of the original supplier's to the custom knife maker. I would call and ask.
McMaster-Carr has "Impact-Resistance Garrolite (CE)" in both brown and black in block sizes. I've used both and it looks & works just like the canvas micarta that BossDog and the other supply houses carry.