These are available at most smaller harware stores or auto parts stores as they are standard 1/2" drive belts but which one you need for your washer depends on the RPM rating of the motor.
Just to clarify for those of us who aren't as experienced as you and some others here, do you mean that a fan belt of the proper size is okay for Maytag wringer washers, but that only a genuine Maytag belt should be used on their automatics?