I just rebuilt the port lights (ABI) on Far and Away. I dismantled them with patience and single edge razor blades. Cleaned the metal extremely thoroughly with a Dremel tool with wire wheel mostly, plus acetone. Obtained new glass from an auto glass shop. (I stayed with laminated safety glass, rather than the stronger - I guess - tempered glass because I wanted the glass to at least hold together if it broke. Make sure the glass is cut as large as will easily fit in the port, so as to maximize sealing surface - my original glass was perhaps a bit small.) On advice of Annapolis Maritime Plastics, who do glass work for high end yachts and were very helpful by phone, I used Dowsil 795 black for the sealant, and used Dowsil 1200 OS primer on metal and glass sealing surfaces. Again on advice, I used lint free cloths fromNAPA, suction cups (McMaster Carr, cheap) to handle the glass after cleaning and priming, and wore rubber gloves, all to avoid contaminating the surfaces.
Honestly, I don't know if all this was necessary or even successful - the boat is not launched yet and I look forward to putting a hard hose spray on the ports - but obviously this is a job one wants to be successful so I went on solid advice and followed it carefully.
Redid the neoprene gaskets too, again McMaster Carr.