I'll put in a plug for one of our sponsors, Pacific East Aquaculture. The are in Maryland and usually have some anemones. Here is the link (offsite) -
http://www.pacificeastaquaculture.com/about_us.html
They do have retail hours at their location, and if you visit in person, you don't have to pay for shipping and will meet lots of cool people.
The place is almost in a class by itself with it comes to corals and such, and it's we;; worth a possible long trip to the store.
One final thought, be sure your tank is well established and stable before you add an anemone. This usually means that the tank has been running about a year.