RareBananas.com - Rare banana plants shipped live to your door.
might have some available (they have a wide selection of both banana plants and banana fruits).
A lot of other members here prefer other types over Cavendish as well. I love grocery store (Cavendish) bananas--they're one of my favorite foods--so I'm anxious to try out some of the other recommended varieties like Gros Michel, Apple/Manzano, Mysore, Ice Cream, Dwarf Namwah, Dwarf Red, Raja Puri, Goldfinger, SH 3640, etc. If I find some I like even more than Cavendish, I might eat a dozen a day.
Here's a link to the current banana fruit selection
at Rare Bananas. They don't have any Gros Michel right now, but they do have a number of other types that folks often recommend.