I have been busy dismantling a fair size building this winter. I started out wearing the goretex combat boot, but common sense got the better of me, and I have been wearing my CF mukluks whether its -25 or even -5. Quite frankly, we only saw the -5 for about 3 days this winter.
There are surplus dealers this way that regularly sell them. The CF ones are quite durable.....I have been retired for just over 10 years and am still using the same pair.
Here is a link to the size 12 liners at a very good price. You'll want more than one pair of liners, especially for that warmer Ontario weather.
http://www.ebay.com/itm/Used-Canadia...item3cdbc5d515