Fred, sorry for the late reply.
The piece from Legend of 1900 that I was talking about is not used in the piano duel . It's called "Tarantella in 3rd Class" by Ennio Morricone.
Do you remember the scene where he's in 3rd class and someone says (in Italian) "hey, play us a Tarantella?" and 1900 says "hey Piasan, what's a tarantella?" The guy hums a bit, and 1900 takes off at 200 miles per hour. The arrangement I have is slightly simplified for the first half, mainly by making the LH just dotted quarter notes, two per measure. Then the second half is more like that performed in the movie, the RH and LH are constant quarter notes, at odds with each other (sounds fantastic!)
The book that I got this in says that this piece appears on the CD soundtrack sold in Italy (so it probably is not available on the US edition CD). By the way, I am in Japan, and this piece is in a Japanese music publication, so I'm not sure that you could get it all that easily... Have you looked at scores for the soundtrack, it might be in one.
If you like the stuff from the piano battle scene, look for "the Crave" by Jelly Roll Morton, which is one of my all time favorite pieces (and I am certain that it's in all the soundtrack score books).