What are the best/cheapest insurance companies (in ontario) that will insure a "high-risk" driver?

It depends how long ago the cancellation for non-payment was. If it was less than three years ago then you would generate four risk points with any company, which means it either the non-standard market or the high risk market (Facility Association). None of these companies sell direct to the public, so contacting them directly is useless as they will not deal with you. You'll have to contact a few insurance brokers in your area and see which non-standard companies they work with (pretty much all brokers work with the Facility Association). If the cancellation was over three years ago some standard companies will still consider you, however you'll still be better off speaking with a local insurance broker and seeing what they can work out based on your information.

Go to a broker. They will know where to look. But expect to pay extremely highly rated premiums if in fact you can get coverage at all. The general principle of insurance is everyone shares the cost of paying claims from their premiums, but in your case you show yourself to be a really high risk and thus have to pay more. Hope this brings home the need to act responsibly toward other users- your past record just shows disregard and outright selfishness.