This film was directed by Joseph von Sternberg and Sylvia Sidney was one of the stars.

On the IMDB site, there are comments regarding how difficult it is to come by this film, but on the very last comment (the posters name is jms blt.. ), someone says they collect old and hard to find movies, and has a copy of this one. The poster says he can direct people to his resource for anyone looking to get their own copy. His e-mail is posted on there. (maybe you could ask him about the other movie you're looking for?) Good Luck!
IMDb :: Boards :: An American Tragedy (1931) :: Where on earth is this film?