I had an old toner box from work that I thought would work perfectly. I had to cut it in half and it was perfect.
They both loved their Valentine's boxes. I felt awful that they really couldn't help since I was using a hot glue gun and an Xacto knife. Not for kids, folks. But they did help pick them out and they helped adorn the boxes with their stickers. ANNDD I got mega hugs for it sooooo.... totes worth it. :)