I am looking for some suggestions/advice to repair my firewall. I purchased the car with a large square cut in the firewall. I was told by the previous owner that the hole was cut to clear a big cap distributor

of course he doesn't have the piece that was cut out and the plate that I purchased to smooth the firewall doesn't cover that area.
Does anyone sell patch panels for the firewall, or would I need to replace the whole thing?
Thanks in advance for any feedback