I second the recommendation for Zimerman/Boulez on DG, it's excellent.
And for something a little less strait-laced you might want to try Francois/Cluytens (EMI). (EDIT:
It actually isn't out of print, I think
.)
As far as I know, there are three different recordings of Bernstein performing this concerto. But I don't know if any of those versions are available at the moment. I only have his live recording with the Wiener Philharmoniker (DG, 1971), directing them from the piano. I wouldn't really recommend that version, except for it's simple joy of playing, it's bit of a mess. His other versions are said to be much better.