Rear lcv storage ideas?

I want to preface this one with the usual no tools are left in my car for any period beyond their immediate use. However,  I have some erbauer boxes that happen to perfectly wedge each other across my tray so they don't slide.  These are good. I also have an ammo can that I use as a grab box for my batteries but without the plastic boxes in it just slides about and beats both it's contents and whatever other tools are in with it to a pulp. I've seen some battery holders either single or as a carrier but the carriers are probably not even as stable or protective as my can and the single ones seem to need screwing onto something which makes them a little too permanent and makes it too easy to leave batteries in them because it'll be fine which we all know it won't be. Whatever I come up with needs to be stable yet easy to remove and when removed leave no particular trace so that as I need the whole volume of the back it is available as necessary. Any clever ideas?