I wouldn't call Java moss slow growing. With co2 and nutrients, I am pulling handfuls out of my tank every other week. Fissidens grows slowly for me in the same conditions as the java moss, but I am not sure how accessible it is to you in Australia.
Fissidens fontanus is my current favorite. IDK what species you may have available to you in Oz, though? Fissidens is a genus found around most of the world, though, and so far I've never met one I didn't like! LOL