You can get anything you want to Australia, it is just going to cost you for shipping.
I recommend checking out www.priorsnowboards.com and picking up one of their ex-demo boards that they have listed. I purchased a new 4WD from Prior last year, but since I am within 4 hours of their factory and was already in Whistler, I bought it onsite. They ship all over the world currently though.
New boots can be purchased online once you know your mondo point size. Go to a local ski boot shop and have them measure your foot. I did this and got a measurement of 26.5-L and 26.0-R. I then bought UPZ RC-10 MP26 boots from http://www.upzboots.com/ which is also 4 hours away from me. Dan shipped them to me and they fit perfectly.
I also bought Snowpro race step-in bindings to go with the boots from the same place. They are designed to work with UPZ boots, but I had a set of bombers TD2 before and I really liked them too.
Like I said before, if you pay the shipping, most people will ship wherever you want. :) Be patient and used stuff will show up on here as well.