Given that the gear is only 1/4 inch wide, howabout doing a bit of watchmaking?
i.e. IF it is possible, bore out the gear and make up two sleeves with opposed tapers, and drill and tap, to make a miniature Taperlock type fitting? Three or four 6BA grubscrews could come into their own.
There probably would not be enough room on one side of the gear to make a Ringfeder type arrangement. You need to apply an axial force to clamp together a male and female split cone.
(A LOT of power can be transmitted by this technique, certainly enough to hold the torsional vibration damper to the crankshaft of a highly rated engine)
Just a thought!
Howard