Contact the map sales person at SC Corvatsch for the map you mentioned:
Riet Gordon
Loestrasse 118
7000 Chur
Tel 081 253 68 06
E-Mail riet.gordon@hispeed.ch
http://www.swiss-orienteering.ch/karten/index.php
Click anywhere on this map, you find orienteering maps in the neighborhood. Then click on 'Bezugstelle' to find the place where to buy it.
They usually send it to you with an "Einzahlungsschein", you pay at the post office in Switzerland when you are there.
The most amazing thing is, how many maps exist in the small country!