Never got on with map cases. They make it nigh on impossible to put the map in my pocket when not in use, and add a barrier between me and the map when in use.
I do have something I was once given that holds a single sheet of A4 very snugly (well, several, but you can only see the top one). It works well, but only for printouts. I mostly use it for notes (e.g. when/where to meet groups, their contact numbers, medical details, etc.) but it has worked for maps.