@RDiaz It might be too late, but Best on Calle Serrano and Denis (Carlos Castillo's good shop off the corner across the street) carry Drake's, and the latter is certain to have a small black and white glen plaid for a wedding.
Hey, Manton, you wouldn't happen to be into spiritualism, would you? I don't figure you're the type, but I have been enjoying the fantasy of you and your acolyte Foo conducting a seance whereby you summon up the shades of the four most recent kings of England (including Edward VIII) to inform them they are sartorial second- or third-raters who look like "stooges"! Then you can do likewise with the ghosts of such Old Hollywood style icons as Clark Gable, Cary Grant, Gary Cooper and Fred Astaire. Not exactly an "Old Hollywood" figure but iconic in his way, you could throw in Frank Sinatra, as well.
Back when I was a young thing, the white shirt was almost a sine qua non of decent dressing. I can't recall my grandfather, who was quite a good dresser, ever wearing anything else with a suit. In my family household we used to refer to them as "regular shirts." I believe some companies made them mandatory wear for executives. I certainly wore them to the exclusion of anything else for dressy attire throughout my prep school and college years. I think it was really only in the late '60s that the colored shirt began to make real inroads.
I note that your bete noire John T. Molloy, writing a mere 25 years ago, says: "Anyone who is selling an important product (which, of course, includes themselves) or appearing before an important group and wears anything but a white shirt is being very foolish."
That said, on the grounds of pure aesthetics, historical precedent forsaken, you may make some valid points. I note that in the past 11 years, despite some almost frenetic wardrobe building, I have purchased exactly one white shirt.