I agree with Mach's suggestion. I used to work for Tandy Leather.

What you want to look for is Vegetable tanned leather.
This is also called tooling leathe. Its designed so you can wet mold it, carve/stamp it, and dye it.
I would recomend looking for Pig skin if you can find it. It has more of a texture and it will even have little pore-like holes where the bristles were. But people don't usually veg tan it because they want a smooth feature-less piece of leather to work on.