Sat Nav Issue…

Hi there, I just bought a 2002 330i E46 (i'm in Australia (just in case)), whilst it has the 'analog' TV unit and onboard computer, the original owner did not buy the Sat Nav option, so it has the screen etc but no Sat Nav. Any idea how i can get the Sat Nav put on to this, or should I just replace - if so what with and from where… Needs to work in Australia…