Apart from NS Guitar Workshop, you can try & buy all Koch products in some selected music stores, in Athens and Thessaloniki.

Specifically you can find them here:

Athens: 

Telesound

Syrou 13-15, 111 47 Galatsi tel. +30210 2220508 
St. Sarafi 27 - 122 41 Egaleo. +30210 5698171

Thessaloniki: 

Zahos Panagiotis

Ioannou Mihail 1- 546 22 tel. +302310-251796

Authorized service for Koch

Christos Daifotis - Crazy Circuit Pedals
Website: www.crazytubecircuits.com