Try your local Ag supply store like a Landmark or Elders. You can get what you need from Bunnings, however they come in small containers that are not cost effective in the long run. The beauty of an Ag supplier is that they will normally give a discout if you ask.
Invest in a good backpack sprayer. If you get serious with your lawn you will find that absolutely need one for all kinds of things like pre-emergent herbicides, plant growth regulators, insecticides etc.
