Here's a couple of drought resistant grass seed available in Canada. I know the US also sells Scotts, not sure if they have it in Australia.
Scotts Canada Home: Scotts Pure Premium Heat and Drought Grass Seed
Buy CIL Kentucky Blue Plus Grass Seed in Canada - Yahoo! Canada Shopping
The CIL brand I think is only available in Canada, but I could be wrong. But, you're right, there is seed out there for areas that don't have that much water.