if you want a printed copy, contact your closest MZ dealer.
or if you dont have anyone locally, you can try dropping a line to MZ-US[
http://www.motorradna.com/]
if a pdf version would sufice you can also search the net, like kazaaK++ or similar. i actually 'found' a PDF version of RT125 repair manual on there, but wasnt able to download as the source user never came back.