The ones I have are pretty old, and I got them from a local store that doesn’t exist anymore. They’re kind of slightly weighted, for lack of a better term almost like a foxtail toy.

You could probably just use standard juggling scarves and get much of the same effect. Renegade Juggling is probably one of the better places to buy juggling equipment.

https://renegadejuggling.com/products/juggling-scarf-23-inch...

I learned using plastic bags. Probably not as uniform in their motion as handkerchiefs, but worked to get the pattern down before moving to balls.