Unwanted grounding from metal screws in metal boxes
I think the clever solution you're looking for is covering the screw with a square of white electrical tape to prevent yourself from touching the screw. 

You could also purchase nylon 6-32 machine screws with a flat head which are non-conductive. 

That only fixes the sympom of the problem, but not the cause. Your excessive static electricity is from low relative humidity levels in the air. Increase it to 30-40% RH and you'll be happier.