HydrangeaPlus has a good selection and will promptly (a few days) reply to your emails; gardensoyvey.com and Gossler Farms are good too.

There are more and you can check them at Garden Watchdog Directory Service of Dave's Garden. Enter the company name in their "Search By Company Name" Box and hit ENTER to see the buying experiences reported by others.

Hydrangea Farm Nursery on Nantucket (hydrangeafarm.com), run by Mal and Mary Kay Condon, is without equivocation the best mail-order source for hydrangeas in terms of product and shipping quality. I have ordered several plants from them and, EACH TIME, I am utterly amazed at how healthy the plants look when they arrive. Honestly, they don't even look like they were just put through the mail!

If you cannot find the variety you are looking for on their website, email them and chances are they will have it!

Hydrangeas Plus is also good but some of my plants have arrived with broken stems and/or substantial wilting. Hydrangea Farm on the other hand never disappoints in terms of their shipping quality.