Bar end fitting kit

[WinstonR]

Can anyone recommend a decent bar end fitting kit?  I bought an Oxford kit from SBS but the internal rubber bungs (not sure what they are called) are too soft so no matter how hard I tighten, my bar end mirrors never seem to feel secure enough.  I also had a cheapo metal fitting kit but it was like cheese and wasn't secure either.  My internal bar diameter is 13mm.

 

Thanks