they really are that simple to make. I'd buy the elastic (it's called satin foldover elastic) yourself and make them. cut off about 5 inches, fold in half, then tie a knot. easy peasy.
I make them and sell them to a few local stores. But what you want to buy is 5/8 fold over elastic. I make them at 9 inches (if you have thick hair make them an inch larger) then cut off a little extra on the ends once I have tied them off. Also make sure to seal the ends because they will fray very easily. I can always mail you a few if you don't want to make them yourself.