Development of custom made shaped plastic or metallic parts would require a mechanical engineer with experience in 3D design for injection molding. There are also enclosures for handheld products, water-proof enclosures, and metallic enclosures readily available on the internet if this is what your undertaking desires. Some makers even provide https://n-ng-m-i-s-n-s-n99764.idblogmaker.com/27708936/detailed-notes-on-electronic-prototypes