i need 1 replacement O ring as well and have not been able to find OEM replacements or the actual size. I took some measurements using a standard caliper (i dont have a metric one). The banjo bolt OD where the O ring sits is .549". The Actual Oring approximate measurements are- OD- .715", ID- .548", and thickness- .088". I have been meaning to check the harbor freight o ring kit but have not had a chance. i will let you know if i find a replacement.