I use a huge orange plastic 'survival' bag which is 7'X 3' in heavy polythene.. It cost the equivalent of $5, is not too heavy and when eventually they do get damaged you can just chuck 'em away (or keep them for boot (trunk) liners when you take garbage to the refuse tip..). They are great fun to slide down wet hillsides on (provided you know the hill well and there are no big drops!)..