What about flying an Australian registered aircraft overseas where no alternate minima is published on the plates?
Then you use whatever is published in their equivalent of the Australian AiP,
Eg. USA, FAR 91.169 c 1 (i) for other than helis, either specified on the plate, or for precision, 600' 2 SM, non-precision, 800' 2 SM.
That would be a lot of different countries AIP's to read through if operating privately?
I guess if it was an airline, the company would have an approved op's manual for the alternate minima's for different countries?