Hi, I am hoping to study at the uni of melbourne, where there is a great international student scholoarship i want to apply for. problem is, it prob won't be enough with travel expenses and everything, so is it possible for me to apply for another 'top-up' grant? is it strange for a PHD student to have two funding sources? anyone know of anywhere i could look for help with this?

Why don't you ask the Uni of Melbourne? This site is mainly for universities in uk.

It's quite common to receive a AUD$7000/yr top-up grant to support an Australian PhD. I think you must align your topic to make the grant organisation happy (a CRC, govt funding body, charity or private company). The minimum grant is barely enough to survive on (~AUD17,000/yr tax-free I think), so it's well recommended applying for top-ups. The Industry related PhD scholarships pay ~AUD24K/yr. Ask your supervisors for help.