Socket Pin-In-Hex Security Screws 12-24 x 1/2" Flat Undercut Stainless Steel Machine. These are not even remotely interested in sticking to a magnet. Better than a Torx screw since those bits are too easy to get and are too common. Even though I had to adjust the price due to shipping increases, these are HANDS DOWN THE LOWEST PRICE OUT THERE!!!
eBay