Terra-cotta tiles can help keep pets cool. If you keep them moist, the evaporation really helps. Flower pots with a saucer underneath might also work. Or you could just squirt or spray a little water on a tile, which is the way I did it. It works surprisingly well.

I did it with a small cat, and she was very happy with it.

This works best at lower atmospheric humidity levels (=better evaporation rates, and more cooling).