In case you're looking for a well-priced ASDL router Down Under, try
AusPC Market. Prices aren't always the lowest, but they have free shipping, and a good reputation.

They have the above mentioned Linksys router for AUD$155 (that's about normal for down here, take note please, US citizens.

)
EYO have the same router for AUD$121, but plus shipping (not sure how much they charge)
If ya want a good walk-in store, PM your location and I'll see what I can recommend.
Cheers
Mick
edit: just reread your inital post.

What you need is a
DLink DSL-504 ADSL Modem/Router, not the 502G. Not cheap , at about AUD$300, but it will do exactly what you want. I would probably go for a separate router and modem, myself. That way if you ever decide to (or can) get cable instead of ADSL, then you can just change modems.