Sorry that I can't answer your specific question, but I might add:
Depending on the iBook, you may find that the screen is not unique to just iBooks or Macs...for instance the screen in my 466MHz is a Toshiba screen, and was used in some non-laptop applications. If you get the screen out, and get past the Apple P/N, you may find that it has some other applications.
What I'm getting at, is if you try to hunt a used one down, you may not have to limit your search to "iBook screen" but may be able to enter a Toshiba or Samsung part number (for instance) for a much broader search.