Are you certain that the leak is coming from the head gasket? I have the same issue, and I finally traced mine to the water outlet at the front of the head. It weeps water, that will follow the front of the head down to the little bit of the block deck that is exposed. From there, it makes its way back to underneath the number one spark plug, making it look like the head gasket is leaking.
I found a easy way to test this.
Park the vehicle on a slope with the rear raised enough to tilt the engine foward, if the leak is at the water outlet the water will show there and not along the head gasket.
