Hello. The small 10mm core plug which sits next to and a bit behind the neutral light switch where the sprocket is, has come loose on my bike 3 times in the last 2500 miles , therefore losing gearbox oil into the right hand side casing where the neutral light switch is. I have tapped it back in each time but it vibrates out after a couple of hundred miles so is clearly just worn out and a bad fit. Does any body have any idea where I might obtain a new one? Burwins do not have one.