Edamame is just another word for soybeans. Soybeans grow here in TN pretty well. The main difference if I remember right is that edamame is picked while the bean is still immature. You should be able to find all soybeans at your coop or maybe even the box stores.

Here is a link that might be useful: Edamame on Wiki

They've grown well for me here in Knoxville. I got my seeds from Kitazawa Seed Company. They have lots of neat asian vegetable seeds and a 100% perfect Garden Watchdog rating. http://www.kitazawaseed.com/