Boot covers. Water proof, insulated. Called the "infantery's best friend".These have been used for something around 30 years or so by the Norwegian army.

As usual, google translate produce some weird results but you get the picture - or at least "a" nice picture of them Boot covers (fotposer).

Being in the home guard I have a complete "individual equipment" in the attic. Good stuff, but heavy and a bit old fashioned - you're talking pre goretex era here. Exept for the lack of a tent, tarp or bivy bag it is all you need for a comfortable night outdoors. I'd trust that kit with my life - but I have more modern and lightweight and less "tacticool" looking gear that I use. With the exception of the boot covers it all stays in the attic untill I am ordered to put it on.