Hello!  As far as I know, blank organ book stock is available from

  Elbert Pluer Draaiorgelbouw
  Noorderweg 32a
  1401 TW Bussum
  The Netherlands
  tel: +31(0)356912186
  email: draaiorgels@pluer.nl
  http://www.pluer.nl/ 
  http://www.bandorgan.com/index.html 
  http://www.bandorgan.com/cardboard.html 

Best regards,

Christofer Noering
Stockholm, Sweden