I don't think many realize this, but you can just take a Priority Mail shipping box and ignore the pre-made folds and chunk them around your shoe box to fit it. It looks Frankensteinian, but I've never had any problems with them being accepted for shipping and it def costs less than a significantly bigger box. For my money, I like getting the free USPS boxes that are a bit bigger than the flat rate boxes shipped to my house. Those work fine w/ shoe boxes, blazers, most things really. You can also do this, then just wrap brown shipping paper around that, so the post office doesn't even know it was a flat rate box to begin with.