If you're looking for walnut, then you would have to find your own blank for USACG. Tommy only sources the tried and tested tonewoods (he's very good at that though) and the best of the vintage construction methods.
Warmoth is an easy bet for the exotics, but if you want something pretty (or anything not quite their standard specs) you'll pay through the nose for it (they upcharge everything) and there is no guarantee it'll sound good. And claro walnut is a bit inconsistent from piece to piece.
You can also speak to Doug at
Soulmate Guitars, who is excellent on the exotic woods and laminates necks as standard unless one piece are requested. While he specialises in set and through necks, he does bolt ons to order. Usually a queue of a month or so before he starts building it, but his quality is worth the wait.