gear sensor o - ring?

[bonova]

My bike is leaking oil from around the gear sensor - Lt side behind the sidestand. I cleaned the thing and re-installed...... but still leaking  
I need a new o-ring - hopefully that will sort it.
Anyone know the size?? by any chance?? looked in the repair manual but couldn't find it....and what with xmas etc, i don't have long to get it from bearing man or the like. will phone KTM tom, but they are a way away.....
thanks!

 

[Dux]

 

[bonova]

 

[bonova]