I know this is an old post but I'll reopen it. I don't know of any place online, but you might check to see if your local University has a Horticultural Club, see if you can contact your local Master Gardener program, and the one I think may be the best chance, visit some Farmer's Markets and chat with people selling flowers. Not all Farmer's Market business takes place at the market. I would expect Seattle to have a Botanical Gardens. Chat with people there.
I think all these give you a fair chance of finding iris that do well locally. As hardy as iris are, I'm not sure that is as important as it is with many other plants, but anyway....
I am so shocked I did not see this post myself. This has been a little bit since you posted. I sure hope you come in and check on this post, because I think I found something really nice!
I sure hope you see this. If you miss it, you can always keep your eye out for other things on Craigslist, or you can simply add a posting for what you are looking for under "Wanted", I am sure there is some elderly person just dying (sorry), just hoping to find you so that you can come clear out all the iris that has taken over.
Wishing you luck in your quest. I always get new Iris locally from folks who want to rid themselves of the excess rhizomes. My next Iris will be a brightly colored Bearded Orange Iris. I doubt it has a name but I saw it blooming this Spring. I loved it!