RE: Trailer roof
Call around any commercial roofing companies you might have in your area, they may have some remnants the would give up cheap, be sure and get white
It goes down with contact cement,, nothing fancier really,, the expensive component is the chemical seam binder/sealer, but you shouldn't need that. you might want some aluminum L-metal to hold the edge down in the wind...
Just a thought, but done right it would last longer than the trailer under it,, Good luck