Depends a lot of how many you're looking to get. If you're doing 50 or less, than your LFS is the best bet. Fish are just starting to come in from the Amazon and the early batches have the highest survival rates. If you're doing more, then you can consider getting them from Snook21 (Aquabid). They're down in Florida so the shipping should not be a killer.
In either case, consider giving the fish a quarantine tank and feed with bbs for a week. None of the fish get fed from the time they're caught in the river to the time they get to the LFS, and maybe to when they get to you. Most fish can handle a 30-day fast but tetras don't have a lot of reserves. A week of fattening up will do wonders for your survival rate.
Willie