WINCHESTER WWII M97 RIOT GUN

[browningautorifle]

the bead blasting would probably would reduce the depth of the proof marks

Silica glass beads don't abrade, that's sand blasting that removed metal. We've done lots of glass beading that cleans out marks and enhances. Use a fine silica glass bead...

Sarco shows a repro, perhaps you could pilfer the ventilated part and spot them together? Don't know how good they are.

Winchester 97 Trench Gun Bayonet Lug Heat Shield With Screws (W97058)

Then there's these, I had one in hand for Mod 12 and they aren't bad. https://www.partsforantiqueguns.com/winreparts.html