(Bolded for emphasis) Be sure to only buy a PLB programmed for Australia!
The EPIRB Hex code has a preprogrammed prefix that identifies the country of registration.
So if you have bought an American EPIRB via Aircraft Spruce, etc. and you set it off, the ground station will route the alert to the American safety authorities who will look in their database and find ?????? Buy this one locally. But of course we all know this, don't we?