Troll the web long enough and you can probably find a replacement. However, if that proves unsuccessful, consider going to a fabrication shop and having them cut out a new faceplate from aluminum using a laser or water jet system. For the faceplate, I would use something in the order of 0.1" thick. You could paint it or polish it to your choice. There is enough residual impression left on the dash cover that you should be able to measure and make a template for the fabrication shop to enter into their CNC machine.
When I did my car up, I wanted to get rid of the ashtray and cigarette lighter and change the hole for the radio to fit a DIN chassis, so I had a fab shop create a new dash cover plate using the old one as a template and just leaving out the appropriate holes when they entered it into the CNC machine. All in cost me about $200 Cdn.
Just an option in case you are unsuccessful with the search for an original cover.
I thought I replied to this yesterday, but see I wasn't successful...
I neglected to mention that my goal with my 142E is to keep it as original as possible. I want it to be a total flash-back to the 70s, and so far have been able to keep very true to that goal. Feeling that body roll going around a corner is all part of it
I appreciate the suggestions, and by the way love what you have done on your car. Really nice work. Right now I've got a period AM radio installed which meets my goals or originality. But I also have this bezel-less AM/FM and feel it would be more fitting the 142E's "luxury" status.