Invest in a proper anti-fog and anti-glare shield and wipe with Rain-X before each race. The shields that come with helmets by default are usually rubbish. Even if you buy a cheap helmet, a good visor can make all the difference.
Or...
http://www.velo.com.au/itemdetailspage/31915
In any case, if all you're using it is for CAMS events, just get one that's Snell SA2010 certified from the US. they're a lot cheaper than the extortion money local mobs ask. It won't come with an AU cert sticker, but you only need one of those for road use. For example those Pyrotech and Bell helmets can be imported from the US for about $100 less. Make sure you don't get an SA2005 helmet, cos you can't use those after 2015. An SA2010 you can use till 2020.