Ah, the AUG is a great gun to be sure. I have a TM though, so I couldn't tell you about the CA specifics.
According to arniesairsoft.co.uk, I think the most recommended hopup unit is the PDC one, but they're very hard to find. The G&P metal ones are the other popular choice.
http://www.airsoftparts.ca/store2/in...ex&cPath=66_80 has the hopup rubbers, but no AUG hopup unit.
I'm pretty sure there are no actual competitive tournaments for airsoft in Canada as of yet, and most players probably want to keep it that way. You'll have to fill out your profile (location at least) so that local players can tell you where you can go to play and to buy gear/supplies. They'll be able to help you out with that FAR better than anyone else can.