I've made PSK's out of SPAM and sardine cans. I use a can opener that cuts the side of the can and not the top, thus leaving the pull tab intact. Fill the can(s) with whaterver you want and expoxy or JB weld the tops back on. They seem to be waterproof and pretty durable. The only problem is if you put something in that needs rotating, you have to pull the tab.

I guess that's a small price to pay for another SPAM and sardine dinner.