Jim Carter sells a reproduction "heater cover plate". However, it looks like it does not have the stiffener ribs in it. You might want to place a Want Ad in the Swap Meet to see if you can find a used one.

Also, place a Want Ad in the Swap Meet for that Hydra-Matic indicator needle. There is a parts seller who frequents the Swap Meet who has in the past posted that needle for sale (and I know he had that needle a few months ago).