Excellent. What I do with such things…
Make a 3D model. My preference is SolidWorks. Any 3D modeling tool works. I’ve never used it so I cannot say but our 3D scanner may help.
Split the model into two parts along the centerline. This creates two perfectly flat edges and, in your case, a clean projection on to the Z axis which means no support / easy to machine.
3D print each slice. Each slice has a flat edge which will adhere nicely to the bed and no overhangs so they can be printed with no support.
After printing, smear a thin layer of acetone on the flat of one side. Carefully press the two sides together. Wait about five seconds. Put the part aside for a few hours. An “acetone bath” will smooth the surface. Spray with silver paint.
The difficult part will be making the model. But, if you need a few, armed a model makes it a breeze to knock out as many as we need in about the same time as making one. And, with ABS, you could easily modify them using heat, metal tools, or acetone.