Cheese curds aren't easy to come by outside Canada. I guess until we have world wide domination with poutine they will stay a uniquely Canadian ingredient.
Mozzarella is an OK substitute but it lacks that squeak to it. A plain halloumi would be something to try as it's a bit closer. Just try to get a mainly cow milk one rather than mixed. It's traditionally goat or sheep milk.
In any case, glad you like what has become the Canadian national dish.
I can't remember if I ever found cheese curds in Australia. I have a friend down there who's very much into her food. I'll see if she knows.
Ignorance, there is a cure.