Maybe Randy's perennials and water gardens. Call and ask before you go. I worked very hard to kill all of mine. It was in a pot in the pond and escaped out the bottom. It was a little version that was cute.

I didn't see any at Randy's when I was there the other day (doesn't mean it's not there, though!) They have a bunch at the Gwinnett Environmental & Heritage Center. I wonder if they would give you a bit.