Lots of clones were based off from standard ATX cases, and the Apple authorized montherboard used in clones used standard ATX power supply connections. Theoretically, you should be able to purchase any PC ATX power supply and it will work just like and have the same soft power characteristics as the original.
Unfortunatly, I'm not intimately familiar with the S9000 machines. But the numerous PowerComputing clones that I handeled used standard ATX power supplies, and sometimes cases.
If I'm wrong, I'm sorry.
You may be in New Zealand, but an american company DTT Service
may be able to help you find the correct parts. As for finding them locally in your location, a good Mac repair shop (even if they are an Apple dealer) might be able to give you advice.