Take it to the cockpit crew if you must. We can always take safe food along for the ride. Your major expense may be buying ice. Nice things to keep on ice might include sandwich fixings. Breads and rolls are usually safe for a day or two with or without ice, but what goes into the sandwich may not be.
Tuna sandwiches can be great and are a good health choice too.
Keep everything for this sandwich in your cooler. If the aisle also has some Infalyte, pick up a bottle or two just in case diarrhea happens. If you don't have access to distilled water, boil your own. This is a very user friendly and packing friendly container type. Heat kills germs.