I would say 90% of the time its not just the operating handle that is broken, but also the SPB hub assembly as well.
You will notice the handle is missing from the right side of this SPB 100 , 4000 amp circuit breaker. Upon closer inspection you can see that the hub assembly is actually broken as well.
The handle is attached by two screws to the hub assembly. You will need to inspect the area where it attaches to determine if the plastic hub is damaged as well. It almost certainly will need to be replaced.