yup- Irontight is in Australia... I have grabbed it from Sprint Auto Parts in the past, but probably just about any auto parts store should have it.

As someone else recomended... just make sure you follow the instructions! You add the irontight at x number of mls per litre of cooling system capacity. You run the engine up to operating temp to circulate the mixture and then leave it in there until you have driven around for something like 12 hours, then you drain it out with the engine hot to allow it to set and refill with distilled water. Sorry, I can't remember exact details, but that's a rough guide! I thankfully haven't had to use it for a few years... cars have been reliable

It does stop the leak pretty quickly though.