Doug,
You may be able to locate a replacement, but need to know some more details to try and help identify the correct original part number for your speedo drive gear.
Needed:
Number of teeth on the driven gear (the piece you have pictured)
Number of teeth on the drive gear (affixed to the transmission output shaft).
You should be able to shine a flashlight in through the hole and get a count of the drive gears teeth without having to tear the transmission down.
Come back and let us know what you have and we can try and help find replacement.
Dan
