There are several options to obtaining a vaguely period knife. Knife shops Knife shows Mail order Make your own Knife Shops Standard knife shops like Cutlery World are generally useless for anything but sharpening blades. Gun shops sometimes carry some knives. I purchased my belt knife at a gun and knife show in San Francisco.
Many gun shows have vendors who also sell knives.
There are also shows devoted solely to knives. Ask around at local gun shops or knife shops for shows in your area. It's fun and simple. This is about the proper temper. Carve a handle, or find a nice piece of bone.