2024T3 aluminum .032" (what you should be using) isn't that hard to work with. I use a vice with aluminum lined jaws, and clamp the metal along with a round form between the jaws. I use a block of wood (piece of 2x4) and a hammer to form the curve around the form. Anything round and hard enough can be used as a form, like a breaker bar or wooden dowel (broom handle?) long enough to extend past the metal. The form should be slightly smaller in diameter than the nosepiece you're trying to fit. Start out with an oversized piece of aluminum, Work it a little, check the fit, then work it a little more, repeating until it fits the curvature. Then mark and trim the excess metal. Use the AC43.13 and Cessna Maintenance Manual for correct rivet spacing and patch dimensions.
