41Y06XT8Z5L.jpgSeems like these would work pretty well...
Vermont American 3 Piece 1/4-Inch Hex Shank Magnetic Nut Setter Set with 1/4-Inch, 5/16-Inch and 3/8-Inch Nutsetters
http://www.amazon.com/Vermont-American-Magnetic-16-Inch-Nutsetters/dp/B00078SJWQ/ref=sr_1_sc_3