Sorry don't know of any other sources for new chain guards.
As for the case it depends on how dingged up it is, if you just used a hammer to beat it out you have probally streched the metal.
I don't quite know how the vert screw hole cover looks like but if it has a lipped flange I would try a bit of 2x4 and cut a slot out to suit the flange and then use that to shape/flatten the flange.
If the gap isn't too large and you arn't really worried about looks maybe a bit of rubber weatherstrip from clark rubber will seal the gaps enough to keep the grass out.
