When we punched a hole in the front of our TT with the tail fin of our 1960 Country Squire, we covered it with a (well sealed) patch cut from scrap of aluminum siding. We made it a name tag.
The don't much do aluminum siding anymore, but a piece of PVC siding material, or any opaque HDPE, might work. Depending on what we were patching, sometimes the one-gallon rectangular tins used for stuff like Coleman fuel, paint thinner, or turpentine were good sources of patch material, although not as well finished as aluminum siding.
