I got mine from a guy called Kev that sells cabinets in Kingswood. He runs two ads each week in the Trading Post so you can get his numbers there. He has quite a few to choose from and is a nice guy to deal with.
Now here's the bad news - he's generally expensive. He will tell you cab's start from about $300-$1500 but when I went there there were some for less, just pretty hammered.
However, since I accquired mine he's begun selling (mainly parts) on ebay under the name "coinoppkev" and you can check out a current auction and contact him here:
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&category=3945&item=6116654927I paid $400 for a fully working generic cab containing Circus Charlie from him. This was before I'd begun browsing ebay (seeing similar cab's go for heaps less, gutted ones less still and the occassional great looking cab go cheaper) or even using this site.
Hope this info helps. I felt like I was in the middle of nowhere when I began this hobby. I started using Mame32 with keys to an X-Arcade, a cab which I got working and now the same cab which I'm re-doing. This time it's not half hearted. Expect Project announcement in a little while fellow Aussies.