Unfortunately it's bloody hard to find a good online store for Australia...
Try international: there's maybe some shops shipping from america or europe to you?
Now about coolant:
I'll try to be as clear as possible here: nothing (short of some gas) can beat the pure distillated water when it comes to store/transport heat (4,2 J/kgK is just way over anything available).
Distillated water (not deionized, not anything else, simply that word), which cost less than 1$/L, is the best thing to put in a watercooling loop. It is easy to pump (less strain on the pump than the propylene glycol (Prestone and the likes)), is available at any grocery or supermarket near you, cost almost nothing, and will not cause erosion (when you use distillated water, there's in fact some ions from the manufacturing process (the deionized water exists because of that), so it will not induce metal corrosion, nor will it protect from it if you mix different metal in the same loop (good way to destroy a waterblock from inside btw)).
Propylene glycol is added to water in cars and trucks because it lower the temperature at which water freezes. Cars running in non-tropical climate need that, while someone living in mexico could run it's radiator with only water and not see any problem. There's a lot of water additive/color, but all in all they just can do 3 things: 1-color the water 2-kill any living thing in your solution and 3-lower your freezing point (only for those containing any glycol).
Reality: 1- Any coloring molecule will, over time (think in many months), precipitate and, little by little, clog and/or stain your block; 2-Many chemicals and ions can do this, and you don't need any specific formula to do a clean job. Native silver is one of the best ions to use, as it is easy to put into water solution (a stripe of pure silver can provide enough ions to kill a small aquarium), does not cost that much (the real weight of the wire/coil is minimal) and did keep my clear tubing-open case and sun exposed loop from turning green; 3- Not necessary in this case.
In short, buy colored tubing and fittings to your like, some pure silver coil (readily available on ebay for like 10$), and use distillated water. Not ANYTHING else. And don't mix metal: stick to copper for blocks and to good brand for rads, you will not be disappointed.