Q: We are looking for a non-conductive  screw that gets close to the strength of 316 stainless steel, ideas?

A: The best we could offer would be our glass fiber reinforced PEEK screws. It has nearly double the tensile strength as natural PEEK at about 22,800 psi. You could also try alumina ceramic screws, but they would be very expensive and although strong, fragile from a toughness point of view.