Thanks for the research guys. I initially tried Google and then Ebay. Ebay had over 2000 listings for GM power window switches and I gave up half way through when I didn't find any with the same mounting brackets. After posting here, I killed some time by going through the remaining listings and finally found four. Interestingly, one was listed for a 70 Buick LeSabre, another for a late 70's Eldorado/Seville, and the final two for 70's Corvettes.
I'll give my old switch a shot of WD-40 and if that doesn't work, I'll try Paul Yates and Daniel's suggestions.