Well, the easiest to do is to find the piano collections and play the top line. That`s what I do. I bought the Easy Piano Songbook online and had it shipped from Japan. Since this is the simplified version for little kids playing the piano, the treble clef rarely has you play more than one note at the same time and it is just the basic melody.
If you don`t want to go that route (i.e. you want it for free) check out the Concert Hall section of www.gamingforce.com
specifically this thread:
http://www.gamingforce.com/forums/showthread.php?s=&threadid=1295
Here you will find transcriptions of a lot of Hisaishi music (and all of it sounds great on all instruments if you as me)
The concert hall of this forum has tons of great anime and video game music that people have transcribed or scanned because they realize how hard it is to get a hold of these works.
Have fun!
