Try the following:
aspell dump master |sort|uniq>wordlist
This is an educated guess, not something I have actually tried.
Alternatively, possibly there is an option in aspell (try "aspell --help" ?) to tell it to do it in english-US. Or maybe there is an option to install the AU dictionary with real words for aspell. If you are on a Red-Hat based machine eg Centos try
yum list aspell
and look for a something claiming to be an australian dictionary then do a
yum install _______(au dictionary)