Seems as though, a panal like that should be pretty easy to make if other options are too expensive, for metal, the roofs of old junk cars can work well, the guy I gave my junk parts car '81 Impala to, cut out the roof panal and used it for panal replacement on his 1987 Chevy 1500 rustbucket which he was given to have crushed because of the bodyrot but, it was still road legal and the bed was the only problem.