Hello David,
A friend of mine, who is a class 5 arms dealer in the UK, made a batch of these smoke dischargers copying my example lying at the front in the first photo. Is my example matching the machinist drawings you have?
There may still be a couple left for sale but not sure. It would be for UK buyers only and they come with deact certificate. Anyone interested drop me a PM and I will get you his contact details.
Cheers,