I was lucky enough to get a copy of maps ( Hema, ubd and many mining lease maps) off my wife's uncle but you can buy the app for like 7$ and it comes with 3 aus wide maps ,
then upload maps you have or memory map disk can be bought online
http://memory-map.com.au/digital-map...australia.html
If you want full aus wide maps Hema on memory map app would be the go as it would get costly to get all areas on memory map maps