Beware, there are two glow plugs that appear to fit, but you have to get the right one for your heater. Going off the old glow plug is not a good idea since the PO likely changed it a few times in the past, and due to the scarcity of glow plugs, may have installed the wrong one.
The two plugs are 194GRN and 194GRNS. The difference is that the one ending with an "S" is with a ceramic core to support the coils. It is also a different resistance so may not interchange.