Cant help with frame design but I can suggest a covering material. Solartex used for covering model aircraft , available in many colours. If you are not familiar with it ,it is a heat-shrink close-woven fabric with heat activated adhesive . An ordinary household iron will do, cuts well with sharp scissors. Scrounge a few scraps that every aeromodeller has under the bench ! Tough, water-proof, with a scale "weave" look. There is also a gloss version if you want a plastic look, with no visible weave, called Glosstex. An old umbrella might be a good source of bits-n-pieces for framework. Hope this helps.
