i dont think they wanted a storage bag , i think they wanted some sort of cover for using during cold weather , if you look at my gallery images you will see our last van covered in snow ,we use a piece of polystyrene underneath the aquaroll and just wrap it in a blanket or padded shirt and take the pump in at night , also make sure the wastemaster is empty ,
We bought two cheapo foam mats (the kind you put under a sleeping bag) from Morrisons. Glued them together like a sandwich. Out of one end we cut a circle to fit on the top of the Aquaroll and the rest wraps around the Aquaroll, secured with a bungee. It's brill! We also stand the Aquaroll on a piece of polystyrene.