I assume you are talking about the "2nd" gear on the main (pinion) shaft.
If tou can give me the tooth count and diameter I can most likely supply it. I ask for that info as gear runs even with the same ratios are slightly different. Particularly the 1.96 gear versions!
If the gears radial meshing teeth and shaft bushing are good, why are you changing gears? The dogs are removable.
Is there a source fro these dogs? The first gear is slightly different in that there is a notch cut out of the dog. Similarilly for the 105-115 gears. Again, same dogs except 1st gear. I've removed several dogs from my Spider gear boxes using shape chisels, a map gas to slightly heat the gear and tapping and prying tools. But, another gear box has to be sacrificed to get the replacement dogs. Does anyone have a source of replacement dogs. The inner bushings used to be available from ALFA.