I don't know if you have a chance to visit the herb fair in Toronto this weekend but I note the list of vendors include seeds of diversity and yet another vendor selling organic and heritage vegetables. I don't know if tomato plants will be available though. Anyway, you can check out the site and contact the vendors directly. http://www.herbalists.on.ca/vendors2007.html

Mason Hogues, north of Pickering had a good selection last weekend. Location is not within the GTA but thought I'd post it anyway.

Thanks Ianna! I sent an email to a couple of vendors so hopefully I'll be able to get them. Plus I've been meaning to go anyway so thanks for reminding me!

Fiesta Farms (near Christie and Bloor) was selling heirloom tomato plants. They may not have any left but they would probably give you their vendor.