We have the Carlisle, Pa swap meets here. Huge show, and like you said, very few Buick items, but they do show up from time to time.
However, it's a great place to buy repo items. I always hit the 'other' A-body suppliers and even the Corvette vendors to search for parts to fit my GS's.
My best purchase EVER was a 2x4 air cleaner I got for $10 in 1982.
The $35 aluminum valve covers were also good finds 'back in the day'.
I did get a '66 GS 4speed carb and intake a few years ago for $50. Sometimes the deals still pop up.