Seeking Valisneria

I hope someone can help me with a problem I am having.  In a flash of 
insight the other day, I realized that the reason the stand of Val. in my 
24" deep tank isn't getting any taller is that it is, in fact, V. 
spiralis tortifolia.  Max. height 7-12", based on my undersized reference 
library.  I am trying to get 6 or 8 specimens of the relatively straight 
Val. species which has leaves about 1/2" wide and 12-24" long.  All I can 
find locally is Jungle, Contortion, and the Val. I already have.

What is the species name of the plant which I am seeking?  My books say 
V. spiralis, although one of the aquarium store people tells me to ask 
for V. retrospiralis.  Does anyone have some of this that they can part 
with?  If you do, and are planning a pruning in the next several weeks, 
e-mail me and I will be glad to buy it from you rather than a store.

Thanks for any help.    Tom