This week? That depends on Australia Post, what you buy and where you buy it from.
Do you want a Corona style like a mincer which is hand operated, single roller like a Philmill 1, which can hook a drill up to or a double roller aka Barleycrusher, Valleymill style?
ESB in Sydney would have some Philmill 1 style. Check their webpage, send an email or make a call.
Goliath's in Adelaide would have a mill of some sort.
Grape and Grain in Melbourne would have a mill of some sort for sale, check their webpages.
As you are a Qld brewer, try the brewshop in Townsville, not sure of their name, something like the Brewer's Warehouse. I do not know what brewshops are in Brisbane or on the Goldcoast.
If you can wait longer, purchasing from overseas is an option. Maybe a local brewer would crush your grain for you in the interim. I bought a barleycrusher from the US. Took nearly three months to arrive, but am very happy with it. Also bought a cheap Bunnings drill to drive it with. With the way the exchange rate is at the moment, overseas purchases are attractive.