Here's the website for Hillside,
http://www.hillsidenursery.biz... They don't do a lot of peonies, just a few species. I bought P. Japonica and Mascula from them last year, both are doing well; P. Mascula has a single bud this year, the Japonica that I got from them looks good but no buds yet. Got a Molly from them a few years ago that didn't survive I ordered bareroot Molly seedlings with no guarantee of bloom color the next year from Brooks and they're doing great.
Another for species peonies is Far Reaches Farms
http://www.farreachesfarm.com/.... I looked at their website just now and am kicking myself--they did offer some larger potted species this year and I missed it. I ordered my first P. Japonica and a couple of Lutea vr from them, all except 1 tree doing well.
Both Hillside and Far Reaches send healthy plants but you do have to baby the little ones more so than the bareroots. Anyone willing to pot them up and garage or basement baby them for the 1st winter would probably end up with nice plants. I don't have an appropriate spot to overwinter pots so mine have to take their chances with the CO winter at a very tender size. It's a testament to the health of the seedlings that any survived!
I have a tree peony that needs a parasol to protect the flowers from the sun. I should buy a nice parasol. 
