hmm..Can you tell us what size/shape of hole, cutout, gouge (or whatever) you have? It would make suggestions easier
But here's one.
Can you use a weatherproof blank plate?
They have gaskets.
Drill and tap holes for 6-32 screws
Cut screws very short
i know trying to save this panel is not worth the effort, but it'd be good to figure out a solution for future similar issues.
is this something i can pick up at home depot?