http://www.mcace.com/shotguninserts.htm that does custom orders and will make up rifled adaptors/inserts in what ever length and calibre that is feasible and ships to Canada!
These sponsor dealers sells the sets in Canada -
And you can also get them from Wanstalls for about $60 more.
This maker http://gaugemate.com/info/sub-gauge-adapters in the states makes them in multiple configurations and sells and ships to Canada and I have had no issues with Customs allowing them. The only issues is that they now seem to take the order and then make them when they have a batch of orders and you can wait up to 4 months for delivery! They are first class products and about the cheapest and very friendly and helpful to deal with.
They are the original makers of the X-Cailber inserts sold by others. They call the set the Pocket Arsenal -
You can sometimes find them on e-bay too!
If anybody is interested in a stainless 7" long .22lr to 12 gauge rifled insert I have a spare that I would sell. It is new never used, I bought it on my last order of some other inserts I wanted and for a buddy. He could not wait and ended up buying the set above which has a .22 Lr in it already.