The website ShapeWays allows designers to sell their 3D-printable products. When a customer orders a design, Shapeways prints it on-demand and cuts the designer in on the profits. A reader emailed us about a nifty iPhone case with integrated 9mm cartridge holder listed on the site . If you are packing a 2-round derringer pistol, this might just be the case for you!
Thanks to Antonio for the tip.