You can find part numbers on this web site:
https://www.bike-parts-bmw.co.uk/bmw-motorcycle
The OE drive belt is 24 82 7 729 767, and it will cost you (at least) an arm and a leg.
Assuming that they ship to Aus, it's worth having a look at carpimoto.it They sell the Mitsuboshi branded version. which I think is exactly the same as the OE one, except for the BMW label - I think they make the one for BMW. I bought one for around 90 euros, and it's currently running just fine on my 2013 C650 GT
Hope this helps.
Mike
