I often wear skinny headbands, and I was brooding over what you could do to make an interesting stitch pattern in I-cord. Beads! The pattern includes (and shows) three variations, but you can let your imagination go wild and change it up however you want. Consider the pattern a starting point.

I don’t usually say this, but this pattern is one of the few that will work in any gauge. Use the yarn you want, the needles you want, and simply knit till it is the correct length. No math required!
Much less than one ball of yarn is needed.