Don Hollingworth has sold his nursery and his peonies will be moving to Oregon this fall. So if you want to order from him this is your last chance to do so directly. It is mentioned in a little blurb in the Kansas City Star's Grow section.
Hollingworth's Peony Nursery
HPS will be taking a bus to Don's on May 18 with stops at a couple of other places including Mitch Jamesons etc iris gardens.
I think you will find that Piet will work with you if he continues the retail side. He mainly does wholesale.