Sorry - OP is you! Original Poster, I think!
Australia in December is a popular destination. Qantas are infamous for being stingy (compared to other OW airlines) on some routes.
But you do have some options if you have enough miles. You could try booking with CX to HKG (from LAX, SFO, or YVR) and then on to SYD with CX or QF. ALternatively, try LAX-NAN and then NAN-SYD.
Others will have other routes/ ideas, but it's a start.