I'm not really a phone expert, I only really know how to work my own SonyEricsson, but provided you have a new-ish phone that can interface with a PC, I would think that the either the MIDI or the MP3 on the main site, which frankie_fan just linked to, would do the trick.
Something to think about, though; I was using the MP3 of the theme song as my ringtone a few months back, and whilst it's cool, it's not actually that well suited to being a ringtone. The problem is that it has that lengthy section of quiet, discordant ambient noise at the beginning, and the main melody doesn't actually kick in for about 15 seconds, which means that a) unless you leave it ringing for ages, you won't ever get to hear the tune, and b) because of the quietness of the opening, you might not even hear it at all.
Since then, I've been using it as my morning alarm tone instead, and it works much better for that.
