Cat5 cable which has RJ45 leads on it is 1 of the commonly used types of leads for dmx. What I assume that you are after is an RJ45 to Cannon adaptor. There's not too much chance that you'll find them in Oz. You can make them up easily enough using parts from Jaycar, Radio Spares, Altronics etc. The wiki has details on pin connections.
If its for the 27 channel boards from Ray Wu that you are looking at connecting at connecting to then it's easy to change over from Cannon plugs to RJ45 ones.