I dropped into my local Learning Express yesterday, and saw this; they say they are one of very few retailers that have it. Comes from France. It's a credit-card-sized rectangle of thin plastic film shaped like a tray, which spins when you push it through the air, balanced on your finger.
They are fragile so they come in a 3-pack. I think they were $5. There seem to be lots of videos of them on YouTube.