For an Eastern iris garden you might try winterberry gardens. They do have a small web site, but many more in their catalog. Mid-America has medians (as does Winterberry). those are my preference but if you have both tall & shorter irises your season is extended.
If you would like Siberian irises to blend with later perennials, try Joe Pye Weed garden in MA. They also have a webs site (I think jpwflowers.com.)
