Have a look at the site I mentioned earlier, MM, and those books may be helpful. A set of French curves will give you templates for most curved shapes. What you could do is draw an outline and photocopy it (assuming you have access to such equipment in your place of confinement). Stick that on a sheet of 10 thou brass and then cut with strong scissors or tinsnips, just outside the drawn line. Then file to shape. This may also be of use...