Yes you can. There are two companies in WA that convert combustion engines to electric: EV Works and Perth Electric Vehicle. The cost varies but is likely to be more than $35,000. There is no government rebate for cars converted to zero emission electric vehicles. Visit the Australian Electric Vehicle Association for more information.
A second-hand electric vehicle like the Tesla Model S, Nissan Leaf and the BMW i3 start from $16,000, rising to more than $180,000 for a Tesla with all the bells and whistles.