I made some replacements for the active aero tray access panels!
I bought some ABS plastic sheets on eBay, 12" x 12", 1/16" thick. It was about $10 USD for 2 sheets, shipped within the USA (YMMV in other parts of the world). 2 sheets is enough to make all 3 flat access panels.
I made templates with card-stock (thick and sturdy) paper, used a pair of tin-snips to cut the main shape out, finished off the curves with a Dremel drum sanding bit, and drilled bolt holes.
It’s a bit easier if you have at least one original panel so that you can trace the shape of the rounded corners when making the template. The corner shapes are the same on all 3 panels, but notice that the corners at the back of the panels are larger radius than the corners at the front.
If you are making an exact replacement of an original panel you already have, and the original is in good enough shape, then you can trace the shape of the original directly onto the plastic sheet using something hard and pointy (a punch/scribe, a nail, etc).
Here’s all the new panels:
I could also cut out a replacement for the center cover (for the jacking point), but I’m holding out for an OEM replacement due to the more complex 3D shape. I don’t have the equipment necessary to make a mold and form a sheet of plastic. A simple flat replacement would probably work fine at covering the hole, but may not lay perfectly flat (I think some parts of the jacking point may protrude a bit?), and would not provide the same exact aero as the original part.