How about a Reynold's Oven Bags? They sell them in different sizes in your grocery store. If you want it even smaller, just go at it with a pair of scissors. They are food grade, and made for high temperatures. Take one, fill it with a quart of water, and then use a Sharpie marker to trace the water line (while still at home). To boil water in the field, fill to the water line mark, tie off the top, and suspend over a fire using the end of the cord/wire you tied it off with.

Another thing to consider is a foil bread mini-loaf pan. Also found in your local grocery store. They are much much heavier foil than typical aluminum foil on a roll. Fold the pan in on itself so it's flat and store in your kit. To use, simple unfold. You probably wouldn't find any holes. It may not be good for many fold/unfold operations, but fold once, unfold once is OK. And once you're in a emergency situation you'll just unfold it once and leave it that way.