Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

So, looking around the internet, I finally found a reference to this page.  You need to scroll down a bit:

http://www.ventix-pages.de/fleischmann/html/tipps.html

It is "interesting". 

It may or may not do what is needed.  For sure it does not address the sealing of the screw holes.  I will try it if I can find some suitable type hose.

But, the original seal was a single piece of some material that appeared to be a rubber.   That would have been able to seal all 4 holes, the two for the glass, and the two for the screws.   Using the suggested technique in the link would mean using some form of LocTite on the screw threads.

The photo appears to show that the plate is used with the dimpled parts fitting together.   I would have thought the thick "washers"  (2.5mm) would need the dimples facing each other concave to concave.

When I find something to use I will report back.  Maybe this, maybe not.