WD 4TB My Book USB 3.0
Delivery to Melbourne looks to be about $19 but free with Amazon Prime.
Click Frenzy means 11% off through Cash Rewards, assuming CR works on Amazon AU site when ordering an international item. Note that I haven't checked this and would be grateful if someone could confirm.
Total if you have Prime and CR becomes $116.70
This HDD is around $190 at Scorptec and $200 at JB. I'm sure it's available cheaper than that somewhere but I can't find anything close to $131.
Edit: Looks like it was $4 cheaper back in August :)
Any idea which WD drive is inside - Assuming blue?