Yeah I had a bit of a look around on gum tree and found a couple but we're still fairly deer, and I live in a county area in NSW and there isn't much around and if I were to by something I wouldn't be able to go and have a look at It , but in saying that still keeping that option open until I'm 100% on the d500Haha sorry Jono :p
As far as second hand skimmers go, the one I've been using for about 2 years now I got off gumtree and haven't had any problems. Was the Reef octopus bh 1000, just had to give it a good clean, nothing can go wrong with skimmers aside the pump going really. And they're usually the cheaper thing to replace so if you're stuck nothing wrong with second hand.
There's also heaps out there but no one seems to want to post them so you really have to be a bit lucky with one popping up in your area