The only Berneke style slugs I have been able to get in Canada are RWS (Rottweil) Exact line. Fiochhi makes them to but finding Fiochi ammo is getting harder all the time.
I could never find any RWS in Alberta even though there are a few dealers here that supposedly carry them. They are imported by North Sylva, I bought mine from places likes Italian Sports in Vancouver, Epps, and Accuracy plus in Peterborough down east. Accuracy Plus also carries the Challenger slugs, which use a similar slug design to the Berneke. If you are ordering from them I would get some of both and see which your shotgun prefers. Shipping is no big deal cost wise, despite what everyone who hasn't ordered ammo by mail posts. These guys also usually have them.
http://sportslodge.ca/index.htm
Best of luck. Let us know how you make out.