I have set of dog boots that have only been used twice. I still have the stuff sack and box. They were a gift, but they are too big for my dog. The webbing on one of them is a little worn, but they are otherwise in perfect shape. They are one of the only boots commercially available that come up high enough to protect your dog's leg if you ski with him/her. They retail for $90; I will sell them for $40 plus shipping. Price is firm.
Small should fit your dog if its paw (weighted) is 2.5" across at the widest point.
I can send pictures of the actual boots if you like.