Check at Crappy Tire.
Not on the regular tool rack, over in the "HELP!" tools.
Look for the socket for doing GM oil pressure switches.
I built one (Yeah! It's nice to BE a machinist!) to get at the pressure switch on my GM 6.5, and found that it was the same size as the injector nozzles on the Jetta.
It might be worthwhile to drag in a 1.9 injector to test for depth.
Could try Princess Auto, too.
Cheers
Trev