I use pizza boxes. My boxes are new (from the pizza place I like the most), the manager has given me one of each size. I love them, they fit on a shelf on top of each other (from small to large). I also have some on end (like a book), when not in use. The pizza boxes are easy to travel with in the car. I do only take a smaller sized box on a plane (people look to see if you're brings dinner with you, but it fits on the tray table so I can work). Good luck finding something that works for you.