There's a place called ABS, their street runs off the one justjap is on.
Also, there is a massive place called Rocket Industries at Huntingwood (2 mins from EC), but I'm not sure how helpful they will be or what brake stuff they have in stock. Rocket are one to keep in mind if you break anything over the weekend.
Not too far from EC is "Race Brakes", they'd be useful but they're closer to Wetheril Park than south Sydney.
If justjap don't have anything you can try a and b motorsports in balgowlah (sp) which is near Seaforth. They stock those brake kits and would be my first stop after justjap. Google their number and call them up. As long as you're heading back over the harbour bridge before about 330pm there wont be much traffic so don't be afraid of that. Avoid the M5 at all costs after 330pm, this may not matter though depending on where you're staying. Are you staying at the chifley with the other VIC guys?