Cornell University's Plants Poisonous to Livestock
University of Illinois' Plants Toxic to Animals
University of Pennsylvania's Poisonous Plants database
The fact that a plant doesn't appear on a toxic plant database doesn't guarantee that the plant is completely non-toxic. However, with a plant so widespread and well-known as bald cypress, the fact that it is not named as being even mildly toxic is a very good sign. However, if you are concerned for your dog, you could pick up as many of the cones as possible and discard them.