The fast, easy way, is to fill out the paperwork for an import permit and buy from Brownells. Figure some time from 3 weeks to as many months or more for the full cycle between dealing with Brownells, dealing with the Import Certificate, getting it back from the Canadian Government, getting it to Brownells, then them getting your order out. There is a sticky around here somewhere about importing parts legally, either here in Gunsmiything, or at the top of Legalese. Worth a read. Our Government does not care so much what you bring in, but the US Dept of Homeland Security and a couple other groups REALLY care what gets taken or sent out of their country, if they think there is a remote possibility it could end up being used against the US folks. Paranoia rules supreme, and the jail time for breaking their laws if caught, is very real.
I suggest Brownells, because they have a track record of actually caring enough for the Canadian customer, that they will go through the bother of the paperwork cycle required to get the product legally exported.
The slow, more expensive way, is to pay someone else to do the exact same thing, for which they (oddly enough

) wish to be paid for their time.
Otherwise you are at the mercy of whatever pops up in the EE, or whatever custom barrel you feel the need for, at the exact same prices that any custom barrel will cost you both to buy and install.
Canadian reality check. You are not gonna likely find the same prices that you see in the Shotgun News, eh.
Cheers
Trev