I looked at buying a similar colored car 66 last year and I ordered cloth and vinyl interior fabric samples from SMS and I believe it would have been a perfect match, I bet they have what you need.
Did your car come from Utah? If so, probably the same car.
https://smsautofabrics.com/
As far as the rear window bay molding, I would try placing a wanted ad on the Riviera Owners message board.
https://forums.aaca.org/forum/73-buick-riviera-riviera-owners-association/
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