OK so this isn't realistic for most....but I will swear by the North Face Himalayan Parka and pants.
https://www.thenorthface.com/shop/mens-jackets-vests/mens-himalayan-parka?variationId=KZ3I spent the last year (I'm back stateside now) stationed in Northern Greenland and while we are issued fairly good cold weather gear, it isn't quite meant for extremes.
As such, I was lucky enough to get a significant discount on the above mentioned coat and pants along with the appropriate boots and supporting gear prior to my arrival.
The gear was phenomenal. I would spend hours outside in -40F temps. When things got "warmer" and calmer I would commonly only wear a t-shirt and jeans underneath and still be too hot. It is worth noting that above 20F the gear was too much and you ended up sweating and overexerting yourself in even simple activities.
In all honesty it depends on what you need the coat for. This one is likely overkill but I wanted to throw it out there. People who buy this outside of practical use (aka lol north face I'm trendy) are not the folks who should own this coat.