Oh, the wonderful joys of shipping fish. Yes, they come to your LFS in little styrofoam insulated carbord boxes with one or two heat packs, in plastic bags of water, about a dozen to a bag depending upon species...
If you do wish to order from somewhere online, there are many things to take into consideration. The foremost is the weather. I once had a shipment of fish delayed by bad weather, the fish sat in FedEx and arrived to me nearly dead and ice cold. Not only will bad weather delay fish, but here right now, it is freezing, and fish that are improperly packed will definately suffer waiting to be picked up.
The first thing you'd want to do is make sure you use an overnight service, counter to counter. Yes it means you'll be inconvienced having to pick your fish up, but it's better than having UPS abuse it. Also will cost more.
Make sure you can get in touch with your seller -directly-. That means be able to email the person who will be handling your fish. Inquire as to how they pack the fish, if they use any meds in the bag (yes fish are given an anestetic when shipped), what courier they use, heat packs, etc. If they can't answer this, don't trust them.
Shipping fish is expensive. You might buy a one dollar fish on line, and pay thirty to get it shipped to you properly. The best thing you can do is find a LFS that might be willing to order it from a repudible wholesaler for you. You might have to put a deposit on the fish and guarentee to buy it depending upon expense (That's what I'm arranging to do with an LFS near me for a Zebra Pleco, which my wholesalers don't offer). Or just keep crusing the shops. Season does have a lot to do with fish availability, some fish onle "come into season" at certain times of the year based on breeding or import influxes.
~~Colesea