The only production-made chiclet keys for Cherry MX (-like) switches I have seen have been on the
Rapoo KX, but those are plastic, backlit .. and it has a uniform 1/4 staggering and only 60%.
As to real metal caps, I think it was "feng" on Geekhack who made Zink-cast keycaps in a contoured cylindrical profile. Zink is relatively easy to cast. They were clear-coated to protect the metal, but once the clear-coat wore off... Zink develops a patina pretty quickly.
There are silver and gold keycap sets on eBay but those are plastic that have been vacu-metallized. They feel like plastic and the metal will wear off. There is a review on Linus Tech Tips...
As to making chiclet keys yourself, the easiest would be to cut them from a flat material that is thick enough and then glue them onto flat keycaps, such as Tipro MID relegendable.
* Instead of pure metal, get laser-cut and laser-engraved black acrylic with metal foil on top. There are lots of firms everywhere that do it for various prices, as well as laser-cutters standing at maker-spaces. I think that material has been available on Ponoko. Cutting and engraving can be done in one process. You just provide a file with your design in a vector-drawing format - with Ponoko cuts and engravings are just in special colours.
BTW, you could also get the wood frame from the same source, made from laser-cut plywood - the edges will be burned though.
* Get everything CNC-router from a metal shop, with letters routed with a superfine routing bit.
* There are firms that do UV-printing on aluminium for electronics hobbyists who need special enclosures. Get the metal printed, then cut at another shop.
* Cut the keys yourself from 15mm wide alu bar. Stack the keys up and clamp them before sanding the edges to a nice radius. No legends though, and you would want an electric miter-saw with blade for metal to do this, otherwise it would be very work-intensive.