Aside from device ID, or maybe if you're using a billing address as something from Australia, I can't see how they would be, you've stated location services are off, VPN will mask the ip.
I didn't even need to use a VPN in my cases between Canada and the US, changing to an account that was in the region that allowed the purchase was all I had to do.
That being said if I changed my Canada account to use the billing address of my US residence instead of my Canadian residence when on the Canadian region, I would get region locked I found, so if you have a primary payment method on file using your AU address you could try temporarily removing or modifying it to have a different address
that's similar to how I do it, change the region and then pay, but some items I've noticed block sale if the originating payment method is in a different region