Hi Marlene, you could make boots from black felt fashioned to the correct size for your dolls, then small amount of fur fabric for a cuff. Here's an article that might help you envision what to do.
You can use felt . http://allcraftsblogs.com/dolls/santa_and_angel_doll_patterns/santa_and_angel_doll_patterns.html This is for a complete doll but you can get the idea from here.
I would look for doll snow boots (the old fashioned rubber style with the button on the side) and paint them black.