I got many of my rhizomes through the Maine Iris Society. Perhaps my want list will reveal my own tastes better. That will take a lot longer. Here are my "haves", excluding the "ones".
Tie for first place with 6 each; Hager, Black
5 each; Kepple, Aitken, Schreiner
4; Tom Johnson
2 each; Lauer, Salter, Goos & Koenemann, Marky Smith, Zurbrigg, Williamson(s), Boswell.
39 different hybridizers overall.