So I have the helmet now and the damaged post is missing the little brass cover that goes over the end of the post. I can see now how they are constructed. (See pictures - Left and right for comparison - with repro cockades and chinstrap).
So either a full replacement (original) post or even just the small cap off of a damaged one would work for me.
I know this is a big ask as these parts are hard to find.
Thanks.
Peter