I suggest O. triptycha while also noting this would be the third sighting of this species at the same location. Given the angle of the shot, the foreshortened image has a different look to the other side-on photos posted of this species, with only the white head of this species just visible.
Hi Ian This specimen was very small - only 8mm long. The other two O. triptycha were larger, 13mm, see: http://canberra.naturemapr.org/Community/Sightings/Details/3371836 So I think this one might be a different species.