Crank mechanism for casement window is malfunctioning

The crank mechanism of one of my casement windows doesn't work properly anymore. When turning the crank, it feels as if the gear is missing some of its teeth. It grabs sometimes, but often it doesn't. I pulled the crank itself off the shaft and confirmed that the issue is *not* simply a loose fit of the crank on the shaft.

It appears easy enough to remove the entire crank assembly and replace it. Can you point me to the correct replacement part(s)? Thank you! :)