I've designed a game which requires 3D geometric pieces. For a prototype, I'd like to see these make from metal, and to look elegant. Who might craft such items? I'm not even sure which profession I might investigate.
A gold smith/jeweler could do your thing from metal and look elegant, but it might be quite expensive.
A 3D printing service would be an ideal solution.
I have no experience with any of the online services available, but as an example Shapeways seems to offer the option to print in a variety of plastic and metal materials, including the most common metals such as Steel, Silver, Aluminum, Gold, Platinum, Brass, Bronze, etc.
If the pieces have an axis of rotational symmetry then I would turn them on the lathe, (or you could search for a local machinist). If not then you could cast them. If you make originals out of wax then you can set them in oil-sand and cast them using the lost-wax method.