Personally I'm a fan of simplicity with function. I took a scrap piece of 2" x 4" 1/4" thick and cut it up to make mine. Welded up and good to go. Simple, and strong enough to withstand countless smashings into boulders
Been tempted to cap the ends, drill and tap, and add a port on it to turn it into a makeshift air tank. Might not hold a lot (~0.86 SCF @ 100 PSIG), but it'd be better than the "tank" on the side of the ARB Air Locker pump.
** hmm, top picture makes it looks like the bumper is kinda warped...must just be a bad picture.