For a one-off item such as you've described, you might want to use an online service such as shapeways and have the part printed with an SLA printer. The results will be microscopically smooth and reasonably strong for your application. If you can create the STL file (or other accepted format) the service can provide a quote. These services can 3D print in multiple types of material. If you required it, even stainless steel is a possibility.