How can I get this?

I had a form of evening prirose with yellow flowers. The plant itself looked like a dandelion with paper thin yellow flowers opening at dusk. The third year, this last spring it did not reappear. Where can I get another one?

http://davesgarden.com/ps/go/588/
Sole, I found it in plantfiles. Dandelion-leaf sundrops. There are 2 vendors.
Sounds cool. Recently, i was hearing about people having "popper parties" in the evenings to watch them open.
Dave