If you're in the northern suburbs you should try Twinkle Tots in Northcote. They have new and second hand furniture. Their website isn't that flash so you'd be best to go in to the store. I couldn't find any cots that I liked until I found one in their store and everyone who sees it comments on how lovely it is. I can't remember the brand off the top of my head but I can check in the morning if you're interested. It was about $600 (brand new) and they included a new mattress as well.

Good luck with your search!