ebay item number: 290384323937.

one thing you MUST make sure of though, is that there is either a key end in the threaded part or a flat piece that can hold the ball joint still while the lock nut is being tightened, else you havnt got a chance. just a simple email to the supplier will do.

thinking about it, i think i got mine from this seller and they DID have an allen key end that makes it easy.

dont be scared to have a go yourself, they are dead simple and will save yourself the £200-300 that a garage will charge you to fit them.