.45Colt: Try: Marstar. Several choices there, that may be of interest. Last Best West, out of Calgary. Another good source. I believe fellow cgn'rs Fingers284 and Garand may also know of saddle makers that might suit.
Failing any of these, you're pretty much going to have to look to the U.S. El Paso Saddlery, might be a good place to start. Well know for their authentic rigs. Followed by Mernickle, and Kirkpatrick Leather. There are others, but any of those three make excellent holsters and gun rigs.
Al