Regarding the gaskets for the "old standard" Lewmar opening port lites, I have 8 on my 87 E34, two of which leak, seemingly at the gasket. I called Lewmar who said they had not made the old standard for many years, had no gasket material and suggested I replace the old standard with their "new standard" opening port lites, at $500 each. Plus they said the opening for the new was the same as for the old so that the replacement was "simple" , not cheap. Apparently the new standard has a similar but slightly different gasket which will not fit in the old standard units.
Christian found an e-bay site in the UK which had several old style gaskets and I ordered one which was advertised as "old standard". It did look like the old standard (had the same "arrow head") but was much too large, 1/2" diameter versus about 1/4 " and would not allow the lite to close. I ordered a smaller version but that too was too large. I am now trying a foam rubber gasket with no "arrow head" so I will have to glue it in place, presently waiting for delivery of several sizes to see which one fits and allows the lite to be closed.