need replacement crank operator

We are moving back into our house after working overseas for 15 years and found that our tenants had destroyed the crank operators on four casement windows (apparently they tried to crank the windows open without unlocking them first). I cannot find anything that looks like this mechanism in hardware stores here. The mechanism has no markings. The cover over the mechanism is 5" wide and 7/8" tall. Do you have replacement parts, and any idea how to remove and replace the crank operator? Many thanks in advance.