I have a bit of a collection going for this game, I quite enjoy it, however, the official ost I just can't seem to find anywhere... I've seen it on eBay once, but that's it. Does anyone have a copy they'd like to sell?

Your best bet is going to be Yahoo Japan. An auction just ended on the 18th of March at 40,000 yen.

N64 + Japanese OST = Uncle Scrooge