I got some small shallow translucent plastic food containers, very cheap from my local supermarket's 'economy' range, with push fit lids. I think they were about 50p each. I cut a bunch of rough squares of aluminium foil and put them in the food container. Exposed rolls get wrapped in a sheet of the foil, which can be squeezed tightly to the roll, and kept in the container. I used to have the occasional instance of fogging of film edges, but never since I started using the aluminium foil.