Thank you all for responding. It turns out I am looking for a #671-186x collector insulation board and it only fits a 1946 Lionel 2020 and 671 engines. The slot for the collector terminal is on one side at the edge on this part, not centered as on the 671-186 that is for the 1947 and newer engine. Send me a message if any body has one for sale. Dave W.
What happened to the original one?
I have re-used turbine insulation plates that were cracked or broken in half. I have found that if you are able to put them in place and reattach the collector assembly, they will stay in place.
They also work fine with little chips here and there, as long as the chips are not too serious.
How bad is the original that you need to replace it? The only supplier that showed the 671-186X was Dew Associates, and sadly it is "OUT OF STOCK". All the other suppliers I have bookmarked, only list the 1947 style in stock. There is an alternative, if the original isn't badly damaged. You can try to use Card Stock, like poster board, and make one, by tracing the outline of the original. Then use an Xacto knife to cut the slits, and use small drill bit to make the screw holes. I have done it once, on the 1947 version, just to get the loco back together, and it worked for me. It is a thought that you may want to try.