Back to the original question. Stores usually get all their new fish on one day, and when the special order arrives depends on whether the supply warehouse has the fish, and gets the order in time to include it. My local chain store gets its fish on Thursdays.
If the plague ridden warehouse doesn't have it, they have to get it from their supplier, and in a massive business like theirs, one fish won't do. They'll have to order in a 300 lot at the least, so that may take longer. But pea puffers are common, so they are likely to have it in the central warehouse.
The health issue? Yeah, it's buyer beware. You get the same fish from most mail order companies. Ones like Wet Spot or Dan's fish are outside the system, and go around the central warehouses to order direct, and that means far higher quality (and often higher prices, but you get what you pay for). I'd order from them in a heartbeat if I were in the US.
But you are in a tough spot for getting quality fish, and with a little luck, you'll be fine.