I wanted something that could hold my pens, pencils, and some other slightly bigger things and that would attach to my toolbox. 

Magnets used: DIYMAG 12Pcs Neodymium Round Base Cup Magnet, 40LBS Strong Rare Earth Magnets with Heavy Duty Countersunk Hole and Stainless Screws for Refrigerator Magnets Office Craft 0.79 x 0.2 inch (Black): Amazon.com: Industrial & Scientific