Turns out I had an old college caddy which was housing all my bathroom cleaning supplies. Now that I only really use Vinegar/ water mixture for all my cleaning needs, the caddy was basically in need of a new job. After wondering around our house finding things that might actually keep two little misters occupied on long car rides, we went for a test run.
I think both boys were happy to a few things within reach. The nice part is if things start flying it's small enough, & has a handle that I can easily take it away.