I just purchased one of these: 110V - 220V Portable Electric Heating Lunch Box Meal Heater Blue
by EtechMart
It's small enough to pack, with room for your cans and can opener inside during travel; it's dual voltage to 220v so can be used internationally with a plug adaptor, and it's got good reviews. I would place your canned food in another container inside the lunch box rather than heating the can. Food needs 2.5 to 3 hours to get really hot, 1 hour to just warm food, so I think it works like a crock pot. About $32 on Amazon.
Despite the older review that said this came with a foreign plug, mine came with an American-style 2-prong plug.