Not sure what it's called but I got a plastic coated one from MGFnTFbitz a couple of years back. Give them a try I'm sure they'll ship one to you.
It's pictured here in this ebay listing
If you look at the ebay listing the part you are after is in the second photograph. If you send Darren a message at mgfntfbitz I'm sure he will know what it is and he will have one.
Like lots of factory black powder coated panels .RUST mine shot .looks as though it might be not needed?
Mine was hanging off . All the rest of the body super clean .