You may be able to find bananas at Lowes, Home Depot or Wal-Mart. They do carry them. Ask. They seem to generally get Grand Nain (the common commercial variety), Robusta (another commercial variety that is also called Valery, Williams, Giant Cavendish or Robusta) and... Dwarf Cavendish (aka Petite Naine).
Those are the ones I've seen. Sometimes they might get a Orinoco (regular or dwarf is difficult to tell).
Stokes Tropicals in New Iberia, LA is a good place to order from.
Bananas
There's always the place here at bananas.org, plants for sale or whatever it is.