Sorry can't help or suggest anything with metal headlight surround. 3D scan and CNC???
In my search I've become a bore on headlight numbers and know you're doing a concourse jobs may want correct lens numbers.
As far as I know (and will happily be corrected) the correct Lens number for RHD is 05:240:700 for the outers and 03:245:700 for inner and are Carello "JOD" lights with JOD marking (diff position, I think, inner vs outer . The bowl has its own number and that determines whether it's got a sidelight or not I guess. "05" denotes RHD and the bowl is marked for right hand circulation too.
I spoke to Classic Alfa as my Montreal shares the same headlights and they confirmed they only have LHD Montreal light with correct markings. In fact Richard Norris is looking for some RHD for his own Montreal. That one you listed is from an early Guilia I think. LHD ones are out there and relatively easy to Ebay etc. I may have some LHD ones but RHD are not easy.