Building the 'expedition' box - looking for ideas and input

[Hodge]

Been looking for a low profile (around 200-250mm high) storage box or two to go my racks but they all seem to be much larger sizes.
Seen anything around?

Might sound stupid. But have a look at some guitar cases going around. If a suitable one was to be found, just rip the original foam casing out and reline it with something of your chooice. One of my guitar cases is un-destructible. Unsure how they would fair out in the weather though.