Hi Bob
I've been getting my buffalo /bison hides from the Leather Guy. they have a good range of colors and specials thru the year. Their web site is theleatherguy.org or at least that's what I have on my address bar when I pull them up.
Great folks, I met them at Sheridan several years back. They carry domestic buffalo from meat farms, the sides are all real consistent.
Happy tooling
Tim