also, I'm not sure how far you're willing to travel, but AquaLife in Providence has a lot of really nice plants, and occasionally get in CRS. They regularly have the Cherry shrimp, and tiger shrimp, too. If you call, you could probably ask them to order some CRS in for you.
Here's the website: http://www.aqualifecentral.com/
Tropic Isle (which Newt mentioned) is very good as well.
And, if you find yourself near Millis (Rt 109, west/southwest of Boston) you should definitely stop in to Ned's. http://unclenedsfishfactory.com/
And, look in to joining the Boston Aquarium Society! There are increasing numbers of folks who keep planted tanks, and bring their cuttings and extras to meetings for the auctions. http://www.bostonaquariumsociety.org/
Best of Luck!