The original steering servo broke down early in the development. I found that a SG90 fits into the mounting bracket easily, just a little filing was necessary. Though it is mounted the other way. I have used a cheap TowerPro SG90 but there are many high end servos that might fit out there.
The A242 is well known for having a large turn radius. By filing out some plastic in the steering column the steering radius was greatly reduced. See the pictures: