I picked up a heavy duty cloth bag a couple of years ago at REI that is made for gorcery bags. It is made by schwinn and has been ideal. It folds flat when not in use, has loop handles to carry to and from your bike that tuck inside and it mounts easily. It did fall off my rack once but when I got home I took some pliars to the metal hooks and now no problems. I think it cost around $40?