I have a similar leak, but it only occurs when the engine is cold. After an evening where temps get down into the 30's, I will wake up to a small puddle. It will stop when the engine runs and gets warm; but it starts again if I open the radiator cap. Have reached the conclusion that it is likely the water pump gasket, but still can't find much about leaks when cold.

 

Very common that it leaks when cold. I'll bet it's the water pump and not the gasket.