As I had mentioned earlier, yes the avionics manufactures have been dragging their feet in relation to this issue due to the US not mandating ADSB in their airspace until 2020. But what this in turn means is that US operators that take their aircraft outside of the US are going to run into the same issues as you are and this is not limited to the operations in the Australian FIR.
The US appears to be the last first world country (could stand corrected) that is mandating the need for ADSB. A lot of people seem to be thinking Australia is going it alone on this, it is not the case. Yes, Australia is one of the first, but others are joining us on the exact same date.
With this in mind, their should of been enough global pressure (even from inside the US from international operators) on avionics manufacturers to pull their finger out and it sounds like there had been some given that a lot of equipment is being released 1H 2014, it misses the December 2013 deadline but is still 6 years earlier than the US mandate.