Look around at what is available but definitely consider Ruff Wear's Bark'n Boots Grip Trex. I found this review from a K9 handler:
I am K9 handler in the Florida panhandle. As you can imagine the extreme summer temperatures are rough on my partner, especially the asphalt in the roadway and parking lots. On a recent mission to we were tasked to assist the Secret Service, during a Presidential visit to the area. This required me to search for a canine boot that would stay in place and be comfortable while worn. Extended sweeps in parking lots and in vehicles which have been sitting in the sun produce temperatures that will burn my partners pads. I found Bark'n boots with grip trex and liked the concept. After the boots arrived I tried them on my partner and with very little adjustment he was up and running. The fit was fine and his working time was increased due to the comfort that these provided. His climbing and running had no effect on them. I wholeheartedly recommend them.