Check with Gilbert Wilds in Missouri or Klehm's Song Sparrow Nursery in WI. They both carry a lot of peonies mail order. Sometimes they list when the plants were hybridized.

Janet

Hi, I've tried to post this three times, so hopefully this works this time!! Betsch's Peony Garden, Charlotte Wilhelm, 740) 775-5246, she has seven acres that used to be a peony farm, she just told us today she digs the plants in early September, and charges $10 for a five eye plant. We almost fell over at the price!! What a great deal!! Hope that she has what you're looking for !
Steph

What varieties of Heirlooms are you looking for? Quite often, you can get them on eBay. A while back I was selling HUGE Festiva Maxima and an old fashioned red on ebay, but that was when I lived in CT.