leaking fork cap o-ring

[Fazer Jim]

Just noticed a dribble of oil around the left fork cap. Seems to be coming from inside the fork itself. Initially I thought I had forgot to wipe up some WD40 but closer inspection leads me to believe the o-ring or rubber seal that lives with the fork cap may have perished. The cap itself is secure enough and the oil isn't coming out at the adjusters. It seeps out through the joint where the cap meets the forks. My forks are pulled up 10mm through the top yoke so the oil is running down the fork top and making it's way along the top yoke like the old Castol GTX advert. However, trying to find a replacement seal is proving a little troublesome. Apparently Yamaha don't sell it? Anyone?