Do you mean turf, as in sod (you know - grass by the meter

), or do you mean turf as in
Torf as in peat?
If the second, any garden center will have it - comes in big 75 litre bags. If the former, start by asking at a garden center - if they can't help you they will probably direct you to someone who can, like a landscape or
Gartenbau firm.
A good place to start looking for garden stuff in your area is:
http://www.garten.ch/firmen/_experte...ertensuche.php
Put in your canton, town or plz, and the type of firm you are looking for.