Hi Bugaboo, we purchased my diamond from Alldiamonds in Elsternwick, Melbourne. They have a website (just search Alldiamonds).
If you give them a call ask for Perry and he will help you find what you want. They specialise in ideal cut diamonds of all shapes and sizes. If you go back through my posts you will see my solitaire pic/s also heart bezel which was also purchased from Perry. What type of diamond are you after e.g shape?
Good luck and let us know how you go, fellow aussie