Ceramaseal
We used to use a product called Cerama-seal on our race engines. It is a liquified glass product that can seal various types of leaks including blown head gaskets. You empty the system, put in the cerama-seal with water, run the engine for about 1 hour and then empty the system and let it sit for a while for the glass to harden. We had one guy who blew his head gasket in California, used Cerama-seal and drove the car back to PA without an issue. It is not meant as a permanent repair, but can be a lifesaver if you need to get the car up and running until a premanent repair can be done.