We spent our family weekend, as you do, in the local Tesco. At one point, my dad turned up with a big grin on his face and a Tupperware container in his hands. Within a couple of hours, this was on my front wall.
All it took was a medium-sized container, a black bin bag, two screws and some duct tape. Now it is secure, water-proof, and has easy access via the lid.
Certainly beats my bulldog clip poster 'stationery hack'. Damn.