Be patient, Im sure someone will be able to help you, the thing is its used in the standard entry falcon which is still a farely new car and ford aus would not keep a stockpile of them in spare parts.
The only option would be to wait until one turns up in a wrecking yard. Actually now that I think about it go to this website, these guys are in Victoria and wreck BAs quite frequently. They might come across 1 or 2 5.4L 3V every now and then.
http://www.ftgautosalvage.com.au/