A seedbag like container for maps, ideally 5x5 (even if this means it's a 2x1 or 2x2 object) so you can store a regions worth of localmaps while the regionmap is being completed.
Alternatively, an atlas, allowing you to bind map pages together with glue and leather.
Just some ideas that occured to me while we were discussing in game mapping, people seemed to like it, thought I would post. Not sure if anything else like it has been posted, as I had no idea what to search for. Map, case, atlas, container all failed obviously.