At first glance, Suzo appears to be much like Happ Controls, with the large catalog and unfriendliness to the small home arcade builder. You have to register to be able to view their catalog.
Suzo is a European vendor, Dutch to be exact, but their web site is in English.
You actualy don't have to register to see the catalogue, you can download it in full through this link: http://www.suzo.com/downloads/SuzoCatalogue2006.pdf or you can download it in parts from http://www.suzo.com/catalogue.php
If you want to buy from them you need a chamber of commerce number. That's the only real requirement. The head-office in Oud-Beijerland, The Netherlands has a "carry-away" counter and my experiences with staff there are that they are both friendly and helpful. Naturaly, this is not an end-user company and video games are not their center point of business anymore. However, they try to help out as much as they can is my experience.
Happ and Suzo actualy merged in 2005. This meant that the Suzo catalogue is now also carrying (some) Happ parts.
Should anyone need help in getting parts from Suzo contact me through http://forum.arcadecontrols.com/index.php?action=pm;sa=send;u=8293