Do these actually exist? Do you mean you want to be a career legal secretary or do this while studying?
If you are doing this while studying such jobs are hard to come by as they prefer to get some who can work full-time, however you can find such work, you just need to check uni-career sites and approach firms to see if they'd like a student to work part time.
If you want to work full time I have seen lots of these jobs advertised on seek etc and often they provide opportunities to do legal secretary courses at tafe etc!