"Not a full list and a bit old now, but here is an international operator list ...
HeliNews - Helicopter Aviation Companies Worldwide ( Helicopter Operators ) "
About that link, it's definitely old, several companies missing and a bunch of others that either no longer exist or changed names. Some of the links don't work either, check out the Heli Union one for example. But yeah it could be a good start for google cross referenced searched or asking around.
Brazil for instance has many more operators than that, between the Air taxi companies and the Oil Offshore support operators...