I am searching for the 90° elbow fitting for the oil pressure sender on the pic below. It just broke of while touching it... can anyone give me a hint where to get this little fella? Thank you guys!

 

Hardware store. HD, Lowes, Menards, Ace, stand-alone local guy, plumbing supply place, etc. Any of them will have this.

Yerbasic 1/8 NPT nipple, maybe 1½" if you can get it, otherwise 2"; and a 1/8" NPT elbow. Remove that intermediate piece and screw the nipple into the block. Turn the elbow whichever way seems to you to fit better.

You're not gonna find the exact original except at a junkyard, which it's on various vehicles of the same general age range and that have a gauge.

 

If you're still in Deutschland, beware of anyone trying to pass off 1/8 BSP (tapered or not) threaded adapters. They cold be more common there, and are not actually compatible with 1/8 NPT since BSP threads are different (55° thread profile, incorrect 1/8-28 pitch, etc.).

Something like could get you back in operation.

 

Yup, sorry, I wasn't paying attention. Amazon is probably as good a way to get it as any.