Harrison's, Dunlap, Tiger Hunt, classifieds, etc. Have you not done any sort of searching?
To me "best" is proper hardness, grain structure, then figure (as needed). You do not want a lot of figure on your first one or two. I trust the long-time regular suppliers of the longgun-making world to be the "best" because if they don't supply good wood, they don't get repeat business. AND they understand the sort of wood we need for good gun making.
I made my first one from a "very economical" piece of Maple from Mr. Harrison, and while longrifle guys aren't impressed by the figure, NEVER ONCE has a "civilian" looked at in in good light and not oooh'd and ahhh'd over the figure of the wood. Most folks don't get to see a lot of good wood. (And non-gun-makers rarely see all the goofups in that gun.)