I keep a couple of spare 9v batteries in my pack. I've been using a blister pack in which two batteries were previously packed. This worked pretty well, but the pack is breaking down. Since I don't want to cause any premature drain on my spares, I'd like to know what options there are for long-term storage. What do you use that works well at preventing them from moving around and keeping them clean? I don't seem to have any spare film canisters, so that's not a good option for me. No pill bottles big enough, either...