Im working on a cardboard pistol,you could get the proportions of the pistol,sketch on to a piece of cardboard,than put another piece of cardboard under it,and cut them out.Those will make the sides of your gun,you can be creative and use anything to fill in the middle.If you use hot glue and cardboard,it will take about 20 minutes to an hour depending on skill.It wont be beautiful,but it will work.