Quartzsite Gathering that were sporting trunks. One in particular looked especially nice, but was more money than I wanted to spend unless the concept proved essential to us.
I used 4 U-bolts to attach the box through a piece of 1/4" Baltic birch that was glassed on both sides to make it easy to clean.
Based on the first short trip, I think this is going to become a permanent addition. It's handy for the contents and in some situations makes a nice extra tabletop in camp.