I really don't understand the Darwin not getting more widely distributed. They are sold through Ball Hort, which is a huge distributor. The plants I got from them were very nice for starter plants. If you go on the Darwin website, you can see a lot of their intros, which are really nice. Or on the Ball Hort website you can look at the whole Darwin catalogue.
If you know of a nursery that grows perennials from plugs or bare root, not one that just receives finished products, why not ask them to grow some of the Darwins.