I now have, and have listened to, Estudando O Samba. Current top 2400: complete.

The checklist:
2403 George Russell Electronic Sonata for Souls Loved by Nature
2444 Marquis de Sade Rue De Siam
2591 Bérurier Noir Concerto pour detraques
2654 Francesco Guccini Radici
2735 Smokey Robinson Warm Thoughts
2848 Artists United Against Apartheid Sun City

There are Sun City CDs on Amazon and eBay, but I don't think I want to pay $90 for it, especially considering the likelihood of its falling out of the top 3000 in the next update. There are a couple of cheap Electronic Sonata discs - but those are of the 1980 re-recording, and I'm a purist. (Yes, my copies of Kontakte, Einstein on the Beach, and Music for 18 Musicians are the original recordings.)

Do things need to be on CD? Or, if so, 'official' CD releases? Finding Warm Thoughts on LP or cassette and burning the contents onto CD should be a cinch.