I haven't ordered a lot of plants myself. There are several good sources for heirloom tomato plants (you have evidently found one of them) but other heirlooms are scarce as plants. SSE sells a few through their catalog (such as peppers & eggplant), but I emphasize "a few". What specifically were you looking for?

If you want to grow heirlooms extensively, you should think about starting your own seedlings. Small greenhouse kits are now as cheap as $300-400, less if you find one on clearance or build your own.

You might also check with any local nurseries (not the big box stores) to see if they might be willing to start your seedlings, and let you buy them back.

darjones@selected plants.com has good,healthy plants and is very helpful. He has a big selection and very reasonable. e-mail him for what you should grow in your area, he grows plants for people all over the U.S. and Canada and will have some good advice for you.
Good luck and GOD BLESS Bill

Also, there's abundantacres dot net. They have tomato, pepper, and eggplant seedlings, as well as some lesser-known solanums.

northerntropics.com