Kayaba shock seal head interchangeability

I got a phone call from a friend of mine who has a 02yz125, he has a problem with the shock seal head leaking. I'm not sure I can help him out because I think yamaha doesn't sell suspension parts alone-if I'm right. Would the seal head off a cr125 be a good replacement? I know the cr125 has a kayaba shock but I'm not sure wether they are the same dimmension (shock shaft and shock body) as the yz.
Thanks!

Thanks!! That's helping me out alot!!