Good luck with getting a timely reply out of North Sylvia! I tried to purchase a couple of Steyr rifles from them a few years ago, and after being told they were ordered and coming soon..... I cancelled the order after a year and a half. No wonder Steyr rifles arent popular over here.
Back to the original question regarding Challenger Slugs, they are available at Stirling Cross in the lower mainland. I purchased a few boxes last week for about $15 per 10 rds, 12 gauge 2 3/4. Velocity quoted on the box is suppose to be over 1600 fps with a 1 1/8 ounce slug! Impressive!