Thought i would just post this, as alot of people seem to think you can not get these sepertetlly, they are on the ETKA but are not marked up they just say 'screw'
My mechanic got one for £4.04, as the thread was a bit knackederd on it and the o ring i put on it was not such a good fit!
I'll get the part number off him next time i am up there!
Just thought you might want to know LoL
take care