Once you have the Bosch part number, you should be able to find it fairly easily in most American parts stores as well. It will be 24 volt and probably cross references with several other part numbers. For example the best source for Mercedes glow plugs is Autozone at $12 each for genuine glow plugs (versus $60 each at other locations). If you google "glow plug test", you can conduct a test with the glow plug out to make sure it is working. No sense in spending unneeded money on new glow plugs if they are not required...
Also many glow plug failures come from poor connections. Toyota uses that voltage resistence strip to get the plugs to glo longer at a lower temp. I got rid of this and uses high gauge wire, it glowed much shorter and always reliably started even at 10-20 below with the truck under 5 feet of snow sitting for days on end (I was in Alta Utah at the time).
I'm looking for a photo of the wire but can't find it... I used I think 12 gauge and standard 10 gauge crimped connectors to the glow plugs themselves. Similar to the Mercedes setup but with larger gauge wire. If you experience trouble starting, glow 2 or 3 times. Do not use ether, use something milder like WD-40 to start it during emergencies... Ether can blow your head gasket or worse...
Cheers, Andre