I just made this pattern up to suit my daughter.

Using 16-inch circular needles;

Cast On 116 stitches

K2, P2, repeat from to end of round
continue in this 2 x 2 ribbed pattern until the headband is about five-inches long, or desired length. Bind off (in pattern).

This is very stretchy and fit a 22-inch head just a little bit loosely.