Thanks for the info on the high temperature aluminum foil tape. That just might work. Maybe I'll give it a try. If the hole in the aluminum is small, I'm thinking putting the tape on the outside - that way the adhesive would just be thru a small hole whereas if you put it on the inside some could seep along all the edges.

I was also thinking about putting water in a plastic oven bag inside a (leaky) aluminum foil container or even just on top of a sheet to heat up over a fire - the aluminum would shield the plastic from direct flame. The question I have is although oven bags are designed to be used in microwaves would heating the bag cause chemicals to leach into the water?