Rear Master Cylinder

Hi, I have a 79 KZ1300A and have a small problem I sure could use some help with, though I guess brakes aren't a small problem. I need either a rebuild kit for my rear master cylinder or a new master cylinder altogether.  At this point it doesn't matter since I cannot find either anywhere on this interweb contraption.  Wow can you find front parts but nothing for the rear.  Am I missing something?  Are there other rebuild kits that will work?  Its the original cylinder and I've had to tinker with it before but now I just want to do it right.  By now the rear brake does nothing to help stop.  Any insight is much appreciated.  -Michael

If your cylinder and piston are OK, you can use the rubber seals from the front kit since they are the same size. The protective rubber boot for the shaft you can buy from me, I have had the press form made and sell replicas.