I have seen people stash them in, mini kegs, ammo box, old radio, beer cans, the fake oil can that xsleo said, pretty much any sort of box or container that you can fit the crap in and mount it somewhere.
I did see one guy who made his own box and then lined it with that packing shit that they use for computers cause water cant penetrate it. Then he would lay everything in there put the top on, squeeze it all together and he had a pretty niffty set up. it was tiny, out of the way looked super clean