By using the freely available User guide for the scanner found here
I was able to find the calibration page part number on page 80, which is 05-0823-000.
Which is easily Googled
Which links to Visioneer (Who makes Xerox scanners) selling it for $5.99
And does not matter if you are in Europe. You can order from the U.S.
I appreciate Joe's effort for searching for you the information's provided to you.