I have one for 8 1/2 x 11 paper. That my MIL gave me when she retired and closed her store. I also have one for 12 x 12 paper that I got at Hobby Lobby.
The one from Hobby Lobby is basically a nicer version then the tutorial one that gregzgurl posted.
I know you can usually get a 40% off coupon for Hobby Lobby directly from their site.