Many gourmet foot shops carry 'European mesh shopping bags' for a dollar or two. Usually they are made of nylon mesh that expands to take a considerable load but rolls up to the size of a golf ball and slips easily into a pocket. In Europe it is pretty common for people to have one in a pocket on the off chance they happen to see something in a market they like. European vendors often charge for bags so carrying your own makes sense. In a pinch most are long enough to act as a binder or tourniquet if needed. I recommend them.