I think Whole Foods has them.

tacklebox does some sort of clambake that you can order

Maybe one of the seafood restaurants. I've used this recipe b/f (minus the lobster). I was using my multi-pot with the steamer insert, so it didn't make quite as much:

http://www.epicurious.com/recipes/food/views/One-Pot-Clam-Bake-366733

For DD's first birthday, we are doing just a small family thing, but I thought it would be fun to do a mini-clambake instead of just the usual grilling. Down at the beach, they have "steamer pots to go" - basically clambakes in a pot that you can do stovetop. (Like this: http://steamerstogo.com/menu/steamer-pots/) Does anyone know of a comparable service locally? (Pref. MoCo / NW DC)