I actually bought my last one from a breeder online. She shipped him to me via Express mail, and I can tell you right now, the difference between a betta raised by a fancier who loves them, and a petstore betta raised on a fish farm, is phenomenal. He did cost me a hefty chunk of change, but this fish is SO healthy, he didn't even do that whole droopy thing they tend to do when you bring them home. (you know the one, where they act like they're just going to die on the spot because you put them in new water) I did check her out first though, reading at other forums about people's experiences with her. (overwhelmingly positive! and she emailed me later to see how my fishy was doing in his new home) If you do end up buying online, look for a live arrival guarantee and refund policy. Most of the time these require you to send the seller a picture of the dead fish in it's bag before they'll send a refund, but it's better than no guarantee at all! (which is what you get from a lot of pet stores) On Aquabid, check the seller's feedback, especially any negatives. If they have a lot of complaints, don't buy from them.

Good luck finding your betta!