I use several different well-tested bags, including one very strong canvas affair, but my favourite is a 45 year old nylon mesh bag that was standard equipment for housewives in Rome who wanted something strong yet small when not in use. I use it for the vegetables that then go into the 12 volt cooler for the 2 to 4 hour drive home. When pressed, I can use the cooler, and two more layers of passive coolers, a 6-pack container inside a 12-pack container, with ice, and get even frozen food home in the summer.