One of my apartment (flat) dwelling buddies has one of these, and he swears by it.
http://store.spruebrothers.com/gunze-sangyo-mr-super-booth-paint-spray-booth-gt03-p455.aspx?utm_medium=cse&utm_source=googlebase
I have been over while he did some airbrushing, and for a small, quiet unit, it works very well. I am sure you could find a supplier in Oz as it it a Japanese product.
Also, whether you airbrush indoors or not, I highly recommend using acrylics, especially Tamiya, which thin nicely with common rubbing alcohol (91%) if you can find it. They clean up with Windex or other similar glass cleaners with ammonia. This greatly reduces the small and also the associated whining noise form significant others!
Chris
A veteran is someone who, at one point in their life, wrote a blank check made payable to "The United States of America," for an amount of "up to and including my life."