Along with the screw
Driver handle itself, these drivers also tend to go AWOL, especially if your purchased a used machine, where the previous owner thought these items would be better left in there garage rather than the tool bag!
This is the fine size, you may also wish to replace the coarse size for the screws in the crank case covers:
9900320000
You may also require the flat head blade:
9900330000
If yours is missing, or just corroded, then bring your kit back to perfection, for such a low price! If you are renewing your entire tool kit, we have all the parts you will need, and at a very attractive price.