I haven't tried this yet, but if you've got a flatbed scanner and a willingness to tear off its cover, you may be able to hack it into something like the mythical HP 4600. This guy also wrote a script that joins the separate pictures together afterwards as well.
I can't vouch for its effectiveness, but it might be an option if you're out of other ideas.
http://hackaday.com/2013/09/27/hacking-a-flatbed-scanner-to-scan-very-large-documents/