boreas
"If it sounds good, it IS good." E.K.E.
Depending how handy and ambitious you are, might want to try removing the pulley and drilling a small hole halfway across the shaft and bearing, then gluing a wire in using the epoxy, sort of like a standard "keyway" ...
Should be easy if you have a dremel tool available. Bonus points if you taper the wire so it locks in place without the glue ...
That might work but the hole in the spur gear is only about 2.5mm in diameter and the gear itself is pot metal so there's a posswibility that the gear might break while cutting the ditch in it.
John