I have half a dozen cat litter plastic buckets that I use for various things: sewer hoses, bungees, tie downs, etc. Once the motorcycles are loaded, there are lots of places to nestle them in. Once we're parked, I put them in the bed of the truck (locking cover) which we rarely drive other than when hauling.
I use low profile plastic bins (I think they call them "under the bed") for tools, manuals, various screws, various types of tape, cables, etc. These go on the "power shelf" in the garage (formerly HappiJac bed).