taigene motor shaft

Taigene motor has a rectangular end on its shaft. What coupler should I use to, for example, connect it to a 1/2’’ shaft?

possibly mount a gear on the output shaft of the Taigene and on the 1/2 inch shaft and mesh the gears together

that way you’ll also be able to control the reduction

The main shaft is 11mm round and the easist method of attachment is; drill your pulley to 11mm (slightly smaller than 7/16) and then use a 3/32 roll pin to secure it to the motor shaft.

A large portion of the shaft has a rounded rectangular shape. Is there any easy way to use that?