Just tripped over this solution (literally) while starting to get organized for the boat in 2 weeks.
An old milk crate combined with 2 bungee cords makes a perfect holder for 6 Plano 3700 cases stacked one on top of another within the crate.
Perhaps not as complete as my Hippo Ranger which holds 4 lano 3700's and has compartments for other stuff; but sure as heck cheaper :-)