Oil Leak on left side on the engine - from the Alternator

Car: Vauxhall Corsa 1.3 cdti EcoFlex 2013
Mileage: 102 K

I have an Oil Leak on the left side (driver side) of the engine, I lose around 1 Litre every 1-2 weeks.

The highest point of the leak I have discovered is from the Alternator - I see oil in the middle of the Alternator.

Please could someone advise or guide me on what seal or gasket I should replace?

 

It’s probably the oil pressure switch, this is fitted at the front directly above the alternator and is a weak point on all Corsa models.
Very easy to fit, remove push fit connector , unscrew switch, screw in new switch and push connector back on. If you have the correct spanner to hand it should only take 1 minute.! Make sure you fit the copper washer or it will leak.!