I think Bluestone will ship mums in the spring. Another thing, you CANNOT cut back the stems on mums until spring or you lessen their chance of surviving. I know, if you like everything neat and tidy it will kill you to do this, but believe me, it makes a difference
Bluestone has the spoon and matchstick mums.
Also, breeders are breeding the perennial out of mums so if you can find someone who has had mums for a long time and get some shoots from them you may have a better chance.
We used to drive up from Maryland's Eastern Shore to Lancaster, PA and there are a lot of Amish farms along the way that sell mums and we'd always stop and get some.
Sadly, my mums have not been taken care of here. They are still alive but I won't get many blooms this year. Well, maybe I will, I just won't be able to see them for all the grass!