Need information regarding vaccination at 18months?

My son is 20months old. He is due for DPT+OPV+HIB booster I which is administered at the age of 18months according to vaccination schedule in India. But at present we are resided in adelaide, Australia. But this vaccine is not scheduled here. Is this a compulsory vaccine? Is there any place in adelaide where they administer DPT booster at 18 months? Or do i need to travel to india for the vaccination?