Any pubs that sell full kegs should have one. A lot normally let you borrow for free when you buy a keg of XXXX etc but maybe you can find one that will let you borrow for a small fee?
Dave at Greensborough homebrew has two he rents out call him 94320283 although with the long weekend coming up they might already be rented...he does have two though!
For the prices I've been quoted from a few local shops, I might go with the coil from kegking and make my own for not much more. I already have a spare esky and tap.
Just put the keg in some ice and you will be right i reckon.
As long as the keg starts cold and you have a container big enough (like a green bin from bunnings? keep receipt and return it after use?) should be right with a few bags of ice.
I use it with a 9L keg in an esky with the lid cut open. Too easy.
May not be too late to ring your local HBS and see if they stock them?