Female bettas USED to be drab looking- have you checked out fancy ones on AquaBid recently? You can find local breeders, as well. My local PetCo actually carries some pretty females...
Or a plakat betta (short-tailed male or female), or a wild type (
Betta coccina is one of my new favorites, beautiful red color!)
www.FishBase.org and you should be able to find some info...