Helmet House, Albany Hwy in Vic Park. You could also try Total Motorcycle Accessories in Vic Park across the road from Macca's. Culleys Yamaha, at the Wanneroo Rd/Reid Hwy crossover in Balcatta. Motorcycle Masters in Kewdale Road, Kewdale have a small range but have cheapies. It's probably worth doing a ring around. I just use a half face in the car, they're pretty cheap. You can try your luck with the scrutineers if you only have the AS1698 helmet and see how you go, feign ignorance and all that. Although you could be spending $55 to be a spectator, but at least you get premium parking !