New England Clam Chowder by mail?
Fresh Lobster Company ships chowder. http://www.thefreshlobstercompany.com/
But what about making it yourself? It's really not that hard. Brooke Dojny's cookbook "The New England Cookbook" has several recipes that you can find on Google Pages:
Scroll down to Page 37, and click on the Thick and Creamy Boston Clam Chowder link for the recipe.
Or check out Jasper White's "50 Chowders" cookbook on Google Books and click on the Contents link and pull down for Clam Chowders.