Hey GU. I just spend the last 3 months down there and let me tell you, it's easy. They hardly sell anything but ISOMs down there because they are freely available and in demand. Just go to any decent cigar shop in Cairns and you'll find 'em. From my experience, there isn't much of a problem with fakes, unless you buy in some of the open-air markets so I would avoid those.
Enjoy - I had Bolivars and R&Js the whole time I was down there.