Have you looked at the Schnee line of pac boots. I believe the pair I have is called the Outfitter. I bought them at least 10 years ago and they fit in a stirrup. They are my go to cold weather boot. I will say to bring a lighter pair of boots also because these are very warm .
I generally wear the same boots when Im elk hunting and its below zero or just above and walking through snow. I like the removable liners and they have always been toasty warm to the point of being a bit too much when walking any kind of distance. Keep a spare pair of liners so that you can swap them out to dry. I have also used Irish Setter boots with good results, warm and good ankle support.
