I frequently stop by this health food store, the closest one to my home, thinking "They probably wouldn't stock something this obscure, but I'll give it a try." and yet they always seem to be able to pull what I need out from one of the tightly stocked shelves. If they don't stock it, it likely isn't available anywhere in Australia. They are also happy to stock brands you recommend. They have locally produced breads, dairy products, dry grains, snacks, teas, oils, sweeteners, etc., as well as supplements and cosmetics. All the staff are very friendly and "know their stuff".
Cons: small - earthquake hazard!, closed on Sundays