I found someone local who's web page says they buy/ restore classic British cars, especially original Mini's. (5 minutes from home to boot!)
Telephoned the owner who said YES- I HAVE A DOME LIGHT COVER!! and we arranged to meet at his shop.
Sadly, he didn't show up at the scheduled time, and hasn't returned my calls since . His small, overgrown yard has 4 Mini skeletons and 2 with tires.
The driver is vertically challenged, and when I first drove her home, I literally had to throw into 3rd gear; the seats had been painted into position and I could barely reach.
This has since been remedied with a rubber mallet.