Dane, you should try ASE in adelaide...
I had my custom catch can done by them, they also make the overflow bottles...
tidy work, i doubt a one off item will be super cheap though...
alternatively, if you made a cardboard template first, almost any fitter and turner/engineering place would be able to make it for you quite cheaply...
eg:
http://www.truelocal.com.au/business/i-and...ty-ltd/richmond