boxes

Looking to work out some ways to store smaller things in my vu ute without having them just floating around while driving. What have people done for this? Things that are too small to be tied down. Any sort of smaller boxes or something like that?

Just an overview of my current setup, I have 2 x SWR-1242D subwoofers which came with their factory designed ported box shown below: I am looking to change them into a custom fiberglass sealed box such as this one: I realize I may get questions like why would you bother and so forth...