... They probably will all leave some gaps that show. ....
Hi Tom,
as
Sportin' Life likes to sing "it ain't necessarily so"!
If one takes a close look at these repro lenses it shows that they have a rim on three sides on the outside. This is where the lens presses against the chrome bezel. However, this rim is missing at the top of the curved edge because the manufacturer has found out that not all bezels are exactly the same. Some may be a little distorted after re-plating so the edge is ground off and one needs to fill in any gaps. That can be done with silicone (German sellers recommend to use "aqua silicone", a product used to seal aquariums) but I agree that this will not last for many years.
As you mentioned the original lenses were heat-molded into the bezel. Well, the same can be done by filling in the gaps with methacrylate (= Plexiglas) the same material that the lens is made of and creating a rim or lip on the inside to cement it in. It is not a quick job and needs lots of attention to details but the end result should last as long as the old lenses.
There is one BIG difference between the old lens and the repro - the old one was colored red throughout whereas the new one is cast in clear plastic and then colored on the
inside. Thus, do not use a solvent to clean it, scrape it, or polish too much, the paint will come off!!