You could always get the daylilies that started the prisms.
Or
These are both inexpensive.
Where to buy daylilies....
Of course where everyone gets daylilies, the
http://www.daylily.com/cgi-bin... lots of reputable sellers there.
For some newer ones and prisms... With fairly cheap prices on newer daylilies.
Maryott's daylilies
http://daylilygarden.net/cgi-b...
If you want a huge selection try Cottage Gardens, you have to know what you are looking for though because there is no pictures.
http://daylily.net/gardens/cot...
Also take a look at the Green Pages on All Things Plants.
http://garden.org/greenpages/b...
I could name many more great sellers!