Doing alot of google lately, and I stumbled onto this site
http://davesgarden.com/
Under Products and Source's, they have a bunch of tools, but more importantly, a tool called PlantScout!
http://davesgarden.com/products/ps/
This thing's amazing!!!
All you do, is type in the name, or any variant of the name of the plant that your looking for, and it searches their database of all their seed sources, and gives you a long list of -all- of them that they have! They even have ratings for these supply companies!
Tho the thing's a bit odd in the layout, when you find a search result your interested in, you click on "purchase", and it transfers you to that sellers website, and usually to -that- items listing!(tho be warned, some of these sellers are on ebay only). If you click on the seller, it takes you to that sellers review/information page from Dave's Garden's website.
This things like the IMDB of plants!