I found them on Ichiban Kan and bought a dozen of them.
The blades and handle were separated in the package, and from what I've seen on other websites the blade should then snap onto the handle. But the back of the package seems to indicate you spun the handle and then the blade would fly by itself. We couldn't get it work that way, so I just glued the handles to the blades. And now I have a bunch of extra blades so I'm hoping with some dowels I can make more.
Here is a video showing how to play with one: