Here are some images of the containers I use for my RIS 1.5 - I like them because they are shallow (and easy to see inside when lid is closed) and the clasps are very rugged and won't pop open easily.
They're made by ZAG and sold by Stanley - do a Search for part #14325 (25 Compartment Professional Organizer). You can take out the little yellow boxes or move them around to make space for larger items.
I believe I bought them from Sam's Club for US$6 each... (US$10 online)
They're thin, light, and my favorite part - look at the back - it has the LEGO pattern - holes and studs. Yes, it's the small things that bring me amusement.