The classic tin plated steel pie tin is a great old-school item. The aluminum version was more common but the traditional, late 60s, solution for a mess kit was to use a Frisbee as a plate/trencher. Completely unbreakable, deep enough for stews, and it does double-duty as a toy and sand shovel. The later point working out well for digging a fire and beer pits on a sandy beach. A quick rinse in the surf and it is ready for food.