I second the recommendation for Sample Seed Shop and Glecklers. Dave, do you need large quantities of each type of heirloom seed, or just a large number of seeds in general? I know I have some extra seeds I could share, but don't have large quantities of any one type.
We just recently added vegetable plants to our Master Gardener's annual plant sale as well. Last year, we didn't have nearly enough cherry tomatoes, although most people didn't care if they were heirlooms or not. It's so hard to predict what our customers will want......