So I live in Melbourne, but I thought I may as well reply anyway. I got a hairdryer with a diffuser and a concentrator (at least, I think that's what it's called...it's the opposite of a diffuser and basically blasts all the air at one place) for $50 at The Good Guys, seeing as I couldn't find a way to get a diffusing attachment on its own. It's called Remington Proffessional Smooth Styles Somethingorother. It has adjustable air flow and heat, and can also blow cool air to set your style.
Unfortunately, it's the only diffuser I've ever had and I barely ever use it so I can't really compare it to anything else.
sorry bout replying now, if u've already gotten one. If not I got a $12 one from PriceAttack. It was a generic one and plastic. Not sure what = nice but it does the job and fits most hairdryers. can't remember the name of it though.
Hope that helps