We are setting up Trans World in the state boards this will take a few days Perth has already been done.these boards will be open to general public and they can also comment without membership. This is a trial only.
$400 would get you all evening in WA 3hours or more
Best sites in wa at least is locanto .. you could try craigs list as well.
other option is to pin up advertising at backpackers round darwin.. specially this time of year
but yea.... your chance of a reply from your add without offering money is next to zero