This is probably not the place to post this question, but I had no idea where to ask it. Where on this site do I look to find gardeners who want to sell plants they need to divide (iris, daylilies)? thanks for your help!

Welcome, @Pinkruffles! This is the place for any questions you have.

Here is a forum that has classified listings. You can look there. I've often found plants I wanted or needed.
http://garden.org/forums/view/...

You can also do a search on a plant you're interested in, and see who has it in their plant list. Many who regularly divide plants have it marked on their plant list that they are willing to share or trade plants.

I've also found that many members here are very generous. If I've loved a plant and say so, I've often gotten offers of seedlings or cuttings.