On amazon in several sizes and colors. I have had these in my cart forever and noticed the price drop. I really want to try them because they are back zip and i have large calves, but I'm having a hard time pulling the trigger on a winter item at the beginning of spring. I also have a pair of UGGS that look almost exactly like these, but they are pull-on.
http://www.amazon.com/gp/product/B00...ce-full-site=1