My first post (from Australia) and it's ref. the parcel shelf and my particular solution.
I had the same as everyone problem; the parcel shelf had been butchered by previous owners removing and shoving back in, plus severe folding and warping from moisture absorbtion over the years. Surprised and frustrated that such a commonly needed and obviously fragile item does not have a readily available remanufactured replacement, I did the following:
1) Removed all the split rivets and traced and cut a new base in 2mm MDF (original was masonite, which would have done as well, but MDF was cheaper on the day), including rivetand bolt location holes. The new base was covered in a thin black vinyl similar to the rear parcel shelf material
2) Used a technique of a Ewe-Tube vintage radio restorer who, when faced with warped or damaged rear panels (usually made of masonite or the same lousy carboardy stuff the parcel shelf is made of) would soak the item in a water/PVC glue mix for a few hours, then press the item between two layers of clingwrap, clamped tightly between two boards and let it sit for a few days to a week. With the cardboard part of the tray now dead flat and rigid, it was easy enough to fold along the original seams. Sprayed the whole with a semigloss black.
3) Soaked a large number of split rivets in a mild acidic solution to etch the stainless steel and then after washing, dipped them in bueing mix, to turn them black
4) re-assembled rail, new vinyl covered base and rejuvenated shaped cardboard original backing.
The radio cutout was a problem as sometime in the past it had been cut overly large. An aftermarket under dash single DIN radio holder in black plastic flipped upside down and trimmed to fit beneath the heater vent sits almost perfecttly in the hole and was bolted to the parcel shelf using existing support bar bolt holes.
Maybe this will help someone