I just went to The Container Store and bought magazine storage cases. They're water proof and they stack nicely. Hope that helps. :-)
What do you mean by case, like a storage box? Or something else? And also I remember a binder once that was speacial made just to hold magazines. It had thin metel rods that were placed in the middle of the magazine and then inserted in the binder. Just thought a Cool Dungeon and/or Dragon Binder meant to hold my back issues would be cool.