I think that you'll be hard-pressed to find any piano sheet music for recent Fish material. It's difficult enough finding classic Marillion stuff (although it does exist).
One thing you might like to try is looking for the guitar tabs that some people have put together, there are links here on the forum. You can usually work out the chords from there and start putting the piano piece together.
As Conan pointed out though - listening to it and working it out is probably the only way you're going to get this particular piece down. Although time-consuming, it's likely to be a better way anyway as music books are generally transcribed by people listening to the music, and then jotting down their interpretations. And I've got some pretty lazy interpretations in my collection