https://en.numista.com/forum/liste_membres.php?o=pays&s=asc&l=tous
I did a quick count - there are about 115 members from Australia.
The list is at the end of the main Forum page, where it says there are 22,711 members currently. As I clicked on 'all' then the list takes a while to load, and click on Country so they show alphabetically. Of course there may be other members from there as a percentage do not give a country when joining.