The only one I know of is
http://www.theflush.com.au/ - and I'm not even Aussie. Not even a Kiwi, either! Last time I looked they seemed expensive, but that has been some time ago.
Try looking for magic shops and not just card dealers. Many if not most carry all the unique decks (or as many as they can find).
Another option you might consider is
http://magiccastle.com.sg - from Singapore, naturally. Their selection is not bad at all and I found their prices reasonable even buying from the US and including the shipping. Better still, they also carry many of the "Asia-only" decks that have become a growing new trend. A handful of deck producers, usually from China, Taiwan, Hong Kong, etc. will special-order a deck from USPC, but have the entire print run shipped to them in Asia, where they'll be sold out at original retail in no time flat. Sometimes they set aside some decks for sale to the rest of the world - and sometimes they don't! Singapore's Magic Castle does get them occasionally and offers them to anyone, anywhere. It's where I got my Bicycle Transducer Night Sakura Edition decks, several weeks before US distribution began.
At today's exchange rate, an Aussie dollar is worth SG$1.06, giving you a slight edge in exchange rates. It used to be that way with the Aussie and US dollars, each valued pretty closely to the other, but these days an Aussie dollar is hovering between US$0.70 and $0.75. What happened? I have no clue. Do you know what caused the rate to change so dramatically? Anyway, you can improve the deal a bit with memberships - they offer regular and Gold, with Gold having a higher discount and the ability to sell your new decks on consignment through the shop.
Otherwise, just put out the call to your fellow Aussies around this forum - there's no shortage of them. Who knows - you might be able to conjure up a buying club between the lot of you and save on foreign orders. Maybe even open a shop!