A while since I've done it, but get permission to land at Moomba. Fuel used to also be avbl at Innamincka and Tibboburra (both drums). Phone numbers are all in ERSA.
Forget about Moomba, unless it's an emergency. Unless you know someone very high up in Santos, you won't have a hope of getting into there. Drum fuel at Innna or Tibbo is your best bet.