Needle Exchanges throughout Victoria will issue new fits for free - no questions asked.
Some chemists sell fits.
Find out where your nearest Needle Exchange or supplying chemist is. If you can't get new fits, you should clean the fit immediately before use by rinsing out twice with clean water,then twice with full strength bleach, then twice again with clean water. At each stage the water or bleach should completely fill the syringe which should be shaken and tapped for at least 30 seconds before flushing.