If you had a way of getting a rubber hose or tube into his pants from the stage or from a nearby table or wall, you could probably use a fog machine. We found that it travels quite well through 6' or more of hose when we were making a hookah smoking catterpillar for a float. You would have to figure out how to get the hose into a leg of the pants or to join it with more tubing already in the waist or pocket of the pants.

I should point out the the fog comes out of a nozzle that is quite hot, but that the fog hitting the air is cool almost right away. The length of hose should make it quite safe, but i would test it. We made a fitting that fastened to the front of the fogger to hold the hose, but to also keep it from touching the fogger nozzle. If you decide this is something you want to try, email me and i will show you the details for this connector.