have bought this kit and it works well but ihave also bought one from poland for under £10 pound and it works jjust as wellit usually the top gasketsthat leak. i connot find the listing for the polihs one anymore asi bought it in july 2018
Last time i needed an unusual sized o-ring i bought one from an online dedicated supplier, i don't recall which one do doesn't really help!
My particular application was fuel pump seal in bottom of a motorcycle fuel tank