Again, the plug should be 22mmx1.5, which would fit the switch from a VW or Porsche:

https://www.pelicanparts.com/More_Info/823959481FINT.htm?pn=823-959-481-F-INT&bt=Y&fs=0&SVSVSI=2100

You need a 92C or higher switch, otherwise the fan will run all the time.