.com search versus .com.au search

[webdude]

Howdy Folks -
Got a question- well, we've got a .com site which ranks not terribly high (pr3) but is very good positioned in the organic search.
We're based in Australia - but when we search for our site in "sites from Australia" it doesn't show up like in the international search.

Is there a way to ethically get a good positioning for the site in both searches?

we know that duplicated content lands us in Google Hell,
so what other options do we have?

any hint in the right direction is very appreciated !

cheers
from the webdude