I did a google of the question and came up with a page or more of information, including companies selling travel insurance. One example is
http://www.vtcinsurance.ca/I have no personal knowledge of this company so the standard disclaimers apply. LOL
The few times I have needed to see a doctor in Canada, I just paid up front and turned it in, to my insurance company when I got home. Medical care is good, but many of the clinics are not set up to bill anyone other than the Canadian Medicare program. One trip I developed a case of contact dermatitis from poison ivy, picked up on our ranch in Oklahoma, but didn't get to be a serious matter till we were back in Canada, headed home to Alaska.
I was quickly seen and given a prescription for the problem, but they first insisted I give them my Alaska Insurance card, which didn't exist. They told me it had to exist as I was from Yukon-Alaska, one of the Canadian territories. The doctor even believed this to be true. Finally I was able to semi-convince the office staff, that Alaska was not part of Canada. Finally they asked me what an office visit in Alaska would have cost, so I told them and wrote them a check for the amount. Stopped at a local pharmacy and got the prescription filled and was on my way north.
Now for anyone that has US Medicare as their primary coverage, as i do now, the rules are a bit different. Read up on it, as it speaks to being in a straight line of travel, from the Lower 48 to Alaska. If you cross in Montana and somehow end up in eastern Canada, on your way to Alaska, and get sick, it is normally not covered. If you get sick in Whitehorse and go to the hospital, then in many cases it is covered but you will probably have to pay upfront and turn in for reimbursement. Like road service contracts, make sure you understand your coverage before you need it, so you can follow the rules to protect yourself in the best manner possible.