The materials are very simple-
A4 cardboard (best) or thick paper. I got coloured card from a $2 shop, or you can get it in a craft or stationery store. If you're using thick paper, it's best to laminate it.
paper fastener - the split type that you push through and open put. If you can't get one, you could try using a twist-tie.
laminating pouch if you have access to a laminator; you could use contact plastic. If you have reasonably thick card, you don't need to laminate or cover it - you can easily make a new wheel when it gets tatty.
You'll also need a pair of scissors with a pointy end (or something pointy), and a design to print on your card. Oh, and a bit of sticky tape.
You can download a free PDF design from my website, www.cathyschords.com