3 Spd Manual Trans. Speedo cable "bullet"

[phlegm]

Guys, Anyone know where i can source a speedo cable insert for my 3 speed Column manual on my 71 C10? I tried a couple of transmission shops and cant find one. I am going to have to replace my clutch at some point this fall once my son starts driving the truck alone and I am picking up gaskets for the transmission, rear main and oil pan .... going to see if I can get it a little less gooey down there while I am at it. The speedo cable is leaking and best I can tell from searches here its not as easy as a single O ring, there is a part that is wore out inside that chamber. Looking for that part.

thanks in advance