Someone who's actually in Australia will be more helpful than me, but I remember I've heard good things about Artemis.
http://www.artemispetfood.com.au/home/
For a wider selection you could have your dog food shipped. Here's a site that ships to all of Australia:
http://petshops.com.au/index.php They sell Canidae, which is decent, but it's not grain free.
Oh, I found a link on that site that is grain free Canidae (never heard of it before now). It looks super expensive, though!
http://petshops.com.au/product_info.php/products_id/1638
Have you thought about overseas shipping or raw?