Don't have a machining recommendation, but consider this:
It is possible for you to make a mold of a nylon rack and then cast a duplicate in Aluminum. The hardest part is melting the aluminum.
Make a flexible
silicone mold, cast a rack from wax, add the sprues and vent holes in wax, make a plaster mold, melt out the wax, pour in molten aluminum. Pewter is a reasonable alternative to Aluminum if you can't generate a lot of heat (melts as around 750F), but can accept a somewhat heavier and weaker material.
You can also make a 2-piece plaster mold if you prefer, but a bit more difficult to get good results.