The small litter pans that Wal-Mart sells are about the same size as the large Reptile Basics hides, which will be good for Bonnie, but for Clyde, I would go with either a medium Reptile Basics hide or a comparably size plastic bowl or container.
If you want to use two hides, then I would suggest taking 2 or 3 water bowls or Tupperware containers at Wal-Mart and using them to gauge the size of tub you will need for everything and the snake to fit in comfortably.
Here is the link to RBI's hide boxes. They should have the dimensions listed so you can get an accurate idea of the sizes.
http://www.reptilebasics.com/hide-boxes