Thanks!
I got my first one from High Country Gardens, but they no longer offer it (that said, let me encourage you to explore Buddleia Alternifolia, if you haven't yet. When I first saw one, it reminded me of a weeping willow with flowers). Found my second one at Lowes or Home Depot a couple years ago -- I was SHOCKED that they would have something so unusual in their collection of standard plants. (I love my Lowes Garden Center folks, but don't expect to find unusual specimens there)
Its page on DG says that it has seeds. I've never paid any attention, really. I deadhead through the summer, then leave it alone for the winter and cut it back in Feb usually. If dried-up flower heads = seeds, I'll be happy to collect some for you if you send me a treemail in October to remind me.