I don't have a pattern but you can make one real easy whatever size you want. Get some poster board or a file folder mark a center line draw one side out cut it, fold it on the center line and mark the other side. Then you can use that piece to make the back side and add a flap if you want one. If you want a gusset cut it how ever wide and long you want and your set to go to lace or sew it.