Does anyone know where I can find a tanned Bison hide that can be used for a blanket for the guest room at my camp?

Depends where you are. Halford's Hides in Edmonton, Canada sells bison hides but they're pricey as all get out. Personally I'd look for someone with a bison ranch and find out when they're getting ready to send some down the road. Perhaps you can buy one and not only will you have a hide (after your taxidermist is done with it) but you'll have a bunch of tasty meat in the freezer.

how much money do you want to spend?

Ebay or taxidermy.net