I just bought a male crowntail betta...I actually saw one female crown betta at Wal-Mart!!!!! She actually looked very good. I'm sorry i don't know any website but i thought that i should share this.
Try looking at Aquabid, I have seen some outstanding female and male bettas on there, just don't know if I wanna pay for the shipping.I'm sure TheMightyPixieQueen, (a.k.a. the betta master) will have some suggestions for you. Good luck!!!
the thing about aquabid betta-wise is that most of the breeders are in thailand or indonesia or whatever. the shipping makes the price higher. but there are sellers in the US. you just have to be patient. at one point, i was looking at that site every night just to see if there were any updates.
where are you from, mademan? there are a few stores here in the SF bay area that sell female bettas. capitol aquarium in sacramento sells crowntail females. picked one up myself. but yeah, just depends where you are.
but ultimately, it wouldn't be a bad investment to buy from thailand. i'm saving up for a pair. you can't beat the genes. i figure, you'd pay the say if you went to a breeder here in the US, or rather take you a while to find some good deals.
Honestly importing is not that expensive to the US... Usually the breeder charges 5 bucks per fish shipping to the US... The transhipper wants around 3 bucks or so per fish for laying the fish over and handling it for you. From there you pay priority shipping to your home.
Try William on Aquabid (siamcrowntail) Nice guy and great fish.