I purchased mine from Forest Farm Nursery about 8 years ago.. Love it. They are out of stock now but they are very good about answering emails and may have some info re restocking. They are a very good mailorder nursery. I have ordered many times from them and plants are packed well, nice size and very healthy.

I think I got a few to start rather reluctantly from cuttings at a nursery I worked at during the 1980s, but am not sure now this resulted in persisting specimens. Otherwise I have a small one here that I bought at a local retail venue not very long ago - apparently somebody was able to get enough of them to grow to make an offering. Maybe if you call independent nurseries there are still a few around.

The Plant Locator - Western Region (2004, Black-Eyed Susans/Timber, Portland) showed Gossler Farms, forestfarm, Colvos Creek and Heronswood indicating they had it at that time.

The first two sources still exist, anyway - as indicated above even where there are no current listings there may be some potential for getting assistance.

FYI it's "species" whether you are talking about one or several.

I have read that the, species, is difficult to propagate, oddly it appears wildly available in Europe. By voloumn and will, or technique, I'm unsure. I've been calling around and some nurseries say they may take cuttings soon, but nothing on hand.