This is actually a Her Universe offering that was available recently at Star Wars Weekends (at the Disney parks in Orlando), according to a friend of mine. But it doesn't seem to be up on the HU site just yet.
Seriously, I'd love to wear this. It's subtle enough to be generally interesting but still obvious to Star Wars fans. (There are other cosplay shirts/dresses at HU but they aren't really my thing, though quite a few ladies adore them.)