Amazon . There are from the other great nations as well.

https://www.amazon.com/Great-Eastern-GE-7712-Village-Headband/dp/B078J1K4XG

It's officially licensed and looks pretty nice. The metal part is a bit long though, and it's not really bent enough to wrap around your forehead all the way. Although supposedly it's possible to bend it more over time since it's not super strong metal.

EDIT: Actually just ended up bending my own headband to fit better, and it was pretty easy. Didn't damage it or anything either.

You can get one on Amazon