Oh, you can find the ZeroStart heaters at just about any Autoparts store.
Installation is annoying as on these heater have to be installed on a frost plug on the back side of the engine. With good access you smack one side of the frost plug with a screwdriver against one edge and it will pivot in the hole and then you remove it. Then you roll the frost plug heater into place and then tighten down the toggle bolt that holds it in place.
The last one I put in was on my 1989 diesel, and it was a pain. Of course it was cheap too....