Almost all of the lfs in our area get their fish from the distributor, sunpet. Sunpet stocks a variety of captive bred Poly's. That said, avarium and aqua imagination both carry Polypterus regularly. You can check out sunpets website to see what they have in stock. Ask your lfs to special order you whatever you need from their stock. If they say they cant, they are lying.
The family that owns avarium are really awesome people. Mike at aqua imagination is also a great dude. I owe them both favors, and vice versa. Let me know if that's not specific enough.