1. Get all the stuff you need: An ankle strap from your surfboard, 4 small strips and a helmet mount (that comes with your GoPro camera).
2. Drill a hole in the helmet mount and the ankle strap and stitch your plastic straps through the holes
3. Voilà! You will now have saved a lot of money that can come in better use while traveling. If you are so lucky to already own a head strap mount you can also use an even simpler solution by following the steps in this YouTube video.