Does anyone have a suggestion on how to repair the "cardboard" firewall cover in my truck? I realize it's 63 years old and probably rotting. But do I have to replace the whole thing or can it be repaired somehow?

This is the only section that's damaged. I'm wondering if the stock rubber floor mat will cover this area...

EDIT: OK, I looked through all eight of my catalogs, and none of them show the original firewall cover I've got. Everything is fiberglass or ABS. I also looked at the online catalogs and included Chuck's Trucks with the same results. So I guess no one sells the original...