Leaky NP203
 

I have a 1977 K-20 with a NP203. I have been going through it and changing seal after seal after seal. On the transfer case where the speedometer cable housing connects to the case there is a union that the driven gear spins in. It has a oil seal that is the same except a little bigger then the one that is in a regular "Bullet" of a automatic transmission. Anyway, I can't seem to find one anywhere, does anybody have any ideas on this matter?