Nylon switch cover plate screws
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.