We found the 9.5" glass plates that we've been looking for at a thrift shop. They were 3 for less than $4.00. We painted one of them black on the back and baked it in the conventional oven for about half an hour @ about 250 F to cure the paint. We will use it for solar cooking bacon.
We will use the other 2 clear glass plates as lids.
To the right you can see one of the 8 nesting black bowls inside the trifle bowl covered with one of the clear glass plates.