Pentatomidae, most probably Poecilometis sp., nymph.
Unfortunately there are many Poecilometis sp. found in your area and nymph are anyway a nightmare to ID. Maybe you find match. Please, not specially the colors and order of the antennae segments. They sometimes are quite distinguish.
http://www.bowerbird.org.au/observations/24608
Careful! There is another one, quite similar:
Theseus modestus! Please, check that one as well...
https://www.flickr.com/photos/108308648@N03/16500205316
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