Is there a light switch cover that will fit the grooves of sheet iron. Or any ideas on how to make a cover to fit
just find a piece of scrap that you used, and lay it on the light switch where it needs to be, and mark it roughly where it needs to lay. from there you cut it out, cut out the light switch hole, and screw it down to the rest of the tin.
Move the box to the flat surface of the metal