I need to find the grounding connector/socket (male) like in the photo for my device, but cannot find what it is exactly called or if it is rather something custom-made.
POAG Potentialausgleich (German: Potential Equalization)
POAG connectors are used for connecting items together for grounding and potential equalisation purposes, often in hospital and laboratory environments, and there is a European standard: DIN 42801, recognised worldwide.
This is a Stäubli POAG connector. For more detailled information on the product, refer to the catalogue: https://ec.staubli.com/AcroFiles/Catalogues/ME_Med-Main-11014109_(en)_hi.pdf or visit the website www.staubli.com/electrical