Odometer help and parts needed

[nxtruck]

Guys,
I'm in the process of trying to fix the odometer in my '65 C10. I'm using the factory speedometer head. The speedo still works and is accurate. However, the odometer hasn't worked since I've owned the truck. I decided to try and get the odometer working, so I removed the gauge cluster and removed the speedo from the cluster hsg. Once removed, I took the back plate from behind the needle off and then could see the problem. The white plastic odometer drive gear that is approx. 2 7/8" long is broken in half. The top half of the gear is gone, but the bottom half is still there.
Does anyone know where a guy could find one of these gears, besides a used cluster assy.? I did buy a new speedo head from one of the parts suppliers, but it reads about 6-7 mph slow, whereas the original speedo was accurate. I'd really like to fix this odometer, if possible. Any suggestions on where to find this particular gear would be appreciated.
Thanks in advance!