I would recommend Aquariums West in DT or April's if you can make the commute. Fantasy Aquatic use to get some nice bettas too but they aren't around anymore
Noah's Pet Ark sometimes have some bettas too and the only place I can find nice females. However, the quality of some of the stock has been going downhill there, so heads up.
Yup April has great bettas for sure but pretty far from your area. Although not specific for bettas at all, Canadian Aquatics is right in your area and they may have some items you may be interested in.