what is this semicircular crank connector part called?
I used the phrase &quot;replacement crank handles&quot; in google and saw lots of places to visit.
One promising site lists handles like shown here:

Picture Source
A model EN 570.2-80-B3.0 sports a 3/8&quot; bore hole and a lever length of 3.15&quot;. You may have to work out adapting the bore with a set screw or craft a D slot using epoxy.