WTB - Super Warm Pants

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I am looking for really warm pants. I am open to different options but they need to have a lot of insulation.

I would like a medium, but if a small runs big that could work.

I have tried to do research but there really isn't a huge market for insulated pants.

SOme of the ones I would like to buy if the price is right are:

Arc'teryx Kappa Pant
Mountain Hardwear Nilas Bibs
North face Makalu Pants
Western Mountaineering Down pants

I need them to be very warm. THe atom LT pants won't cut it. I live in the Colorado Rockies at 10K Feet and I do a lot of winter night photography. Ever since I upgraded my jacket to the amazing Arc'teryx dually I now feel my legs freezing. I think the dually does such a great job up top that it exaggerates the cold on my legs.