I have bought seeds from all of them and they seem to work.
All are from Canada
www.dominion-seed-house.com
www.veseys.com (best)
www.ttseeds.com
Good luck
Ken

Hi,
Guru Garden would be a good place for next year. But if you are still looking for some of the species seeds for this year then I would try:
Gardens North - they have I. auricoma, I. capensis, I. balfouri
I would try Chiltern's - I know they have some but their website is hanging on my pc - I. hochstetteri, I. textori, I. roylei
B-and-T - the big French seed site might also have some.

I would think you would have better luck with the British and Canandian sites. Most of the American sites have the F1 hybrids.

Good Luck!
Sheila