I understand "silverrat23" posted recently M570 deal from Amazon US (https://www.ozbargain.com.au/node/131028). But I found this could be easier to get it locally, so that you will have local 3 year warranty if you ask Officeworks to beat MSY $45 price so you get further 5% off to make it $42.75. I personally just ordered one from Officeworks and will get it tomorrow.
Logitech is selling this one on their website for $109.95 with free shipping (http://www.logitech.com/en-au/product/wireless-trackball-m57…).
From users' experience and also from Logitech website, it says battery can last around 18 months, what a super powered mouse and it is wireless.
It uses Logitech® Unifying receiver—the tiny, wireless receiver that stays in your laptop and lets you add compatible devices as you need them.
Another good thing for this mouse is it is ergonomically designed and it use this trackball to reduce your wrist movement. The Logitech M570, is controlled with the thumb while the fingers remain motionless over the buttons and scroll wheel. The ball is extremely lightweight and easy to control.
Please be advised that minimum order to qualify free shipping from Officeworks is $55. You may need order something else to make up to 55. For me I ordered another SanDisk 16GB Ultra Class 10 (30MB/s) SD Card. Officeworks sell it $26, but after matching price from MSY $17, it becomes $16.15. Still a good deal.
This is my first deal. Hope it is useful for someone like me, as I am experiencing wrist pain after I use a couple of hours my normal Lenovo mouse. I am afraid I may hurt my wrist permanently, that is why I decided to invest some reasonable money on this kind of Ergonomic mouse. It may take some time to learn how to use Trackball mouse, but I reckon it is worthy to have a try.
Usually officeworks don't price match MSY.