Oil filter /cooler assembly leakage

Guys,

today I found my oil filter assembly / the aluminum part under the oil filter - leaking between the separation flange towards the cooler connection. Seems to be there are two O-ring sealers in, I didn´t take it apart because I have no spare in the pocket ( I´m German). My car is a ´94 BRM, does anyone know the correct size of the O-rings for me to check it out where I´ll get some over here? Hoping metric ones will do the Job...thanks for help.