Check out the Balenciaga Shopping threads section. Listed below are some places to shop online. The stores you mentioned usually don't have many bbags on their sites. You would need to call. This list is copied from the shopping thread:
Balenciaga has some rule about not having their bags listed on the web, through their big department stores anyway. If you call Neimans, Nordstrom, Saks, Barneys, etc., they will be glad to help you with a bbag!