Wirelizard, perhaps that Saro Cloud, or something very much like it, could be carved out of high density foam, and then some thin ribbed bendable plastic from a train model supplier like Plaststruct could be wrapped over the carved foam. Maybe there could be a cutout area in the foam so that it would be possible to see through the cabin via clear plastic windows. Perhaps some bits such as the wings and cockpit windows could be taken from another model kit.