When I'm making cases for charity, I just buy a yard of 2 different fabrics. The case body will be 26-27 inches, the contrasting band will be 9-10", depending on how accurate the cut is. I usually have something to get the 3" contrast strip from my stash. If I want to give them as a gift, I call them "flip flop pillowcases" since the fabrics are reversed in the cases.