Every time someone touches any of my light switches they get a static shock. I know the root cause is the humidity is too low, but until I fix that, I heard that nylon cover plate screws (vs the usual metal ones painted white) would help this problem (I guess the theory is that the screw is touching the box which is what the person is "discharging" through). So I was going to pick up some of these to test it out, but I couldn't find them in hardware stores or on Amazon. There must be a reason these are so hard to find - is there a reason not to use these? Or can anyone recommend where I can buy them?
A new trend is switch plates which snap on, and do not use cover plate screws at all. That is worth looking into.
Of course, none of that will solve the underlying static problem; you'll just get nailed instead by the next metal thing you touch. I would want a metal cover plate isolated by a 1 megaohm resistor to safety ground, because that would actually dissipate the charge.
And of course, make sure your safety ground and grounding electrode are tip-top to be sure you aren't actually getting bit by mains current. That is somewhat different in sensation, and also does not disappear in high humidity.
Shopping is off-topic, but...
Easy to find if you use "plastic" instead of "nylon" in your Googleing: plastic switch plate screws