Tree Peonies Sale at
All available Japanese tree peonies and herbaceous peonies are priced 25% off and shipping is only $10.
I do not know how good they are but I ordered 3 tree peonies and 5 sarah barnhardts anyway.
The Heartland Peony Society Sale is coming up in early October. I know there will be a good supply of Japanese tree peonies at that sale. Unfortunately you have to attend in person to make a purchase, you can't mail order or anything like that.
Here is a link that might be useful: Heartland Peony Society fall sale