Use the strong Aussie dollar to buy cheap phones from the UK! the Motorola DEFY Mini Sim Free Smartphone - Black is currently on sale from Amazon UK:
Motorola DEFY Mini Sim Free Smartphone - Black

Motorola DEFY Mini Sim Free Smartphone - Black: Electronics

it's currently £59, but with the strong Aussie $ that's now dropped to about $86 - probably close to $90 with postage. Make sure you check this thread: Bank account that's great for overseas travel & online shopping! Rewards transaction account - as it offers a bank account where you don't have to pay exchange fees for international purchases.
Product Features and Technical Details

Product Features

  • IP67 rating allowing the Defy Mini to be submerged in up to a metre of water for 30 minutes without failing
  • Scratch resistant Corning Gorilla glass, dustproof and shock proof
  • 3.2” HVGA display, compact size and long lasting battery
  • Rear- and front-facing cameras for easy sharing
  • Social networking, email and outdoor pursuit apps

Technical Details

OS: Android 2.3 (Gingerbread)
Form Factor: Capacitive Touch Candybar
Bands/Modes: GSM 850/900/1800/1900
UMTS 900/2100, 850/1900, 850/2100,CDMA
HSDPA 3.5, EDGE class 12, GPRS class 12
Dimensions: 109 x 58.5 x 12.5mm
Size: 71cc
Weight: 107g
Display: 3.2” HVGA 480 x 320, 262k TFT (Corning Gorilla Glass)
Memory1: 120MB end user memory. Expandable up to 32GB
Processor: 600MHz
Messaging: SMS, MMS, e-mail (SMTP, POP3, IMAP), IM
Audio: Voice codecs (AMR-NB/WB), music playback (AMR, MP3, MIDI, AAC,AAC+, eAAC+), ringtones (AMR, MP3, MIDI, AAC, AAC+, eAAC+), voice recording (MPEG4, H.263, H.264,30fps@VGA)
Video: Capture/Playback (MPEG4, H.263, H.264, 30fpsHVGA) /Streaming
Camera(s): 3MP, FF, resolution up to 2048 x 1536, LED flash, digital zoom. Front-facing VGA camera
Connectivity: Micro-USB charging & data (USB 2.0 HS)
3.5mm audio jack. Corporate sync, FOTA, NGP, OMA DM, DLNA
Bluetooth: 2.1. Profiles: A2DP/AVRCP/HFP/HSP/OPP/SPP
Browser: Android™ Webkit, Adobe Flash 10.1 supported (available as download from Android Market)
WiFi: 802.11 b/g/n
Preloaded apps: Google Services (Google Maps, Google Talk, YouTube, Google Mail, Android Market, Google Navigation, Google Search), Facebook, Twitter
Battery: 1650mAh
Talk Time 2G/3G3: Up to 580min (9.6hrs)/540min(9hrs)
Standby Time 2G/3G3: Up to 420hrs (17.5 days)/360hrs(15 days)
Special features: Water resistant, scratch resistant and dust proof, MOTOSWITCH UI (2.0), Gravity sensor, light sensor/proximity sensor, eCompass, GPS/aGPS
Other: eCompass/aGPS