I have moved to another country and left my 1TB WD HDD back at home which I was using with Time Machine to backup my device. I've used this device for years so it has backups from my previous MacBook. I am going to be working at home occasionally and since the Air has no CD drive I have no way of making backups which I now need. What is the cheapest (but also suitable and working) device I can buy? I'm happy to buy second hand from eBay or the likes. My SSD on my MacBook Air is 120GB so I guess I should be looking at a 500GB drive at a minimum, right? Also, I should point out i'm in Australia so shipment to Australia is required.
Surprisingly enough there are online electronics companies in Australia which will courier your device to your door. One well known bargain online retailler is www.kogan.com.au You should be able to find the right deal for you, after all Straya is not exactly a third world country despite the best efforts of the Coalition govt.
Get a $5 USB-to-SATA converter and chuck it into whatever 250GByte-or-larger HDD that you can find (usually one can get old HDDs for free from some chum who's scrapping his old PC). http://r.ebay.com/Xb65eB