casting parts at home

+1 for 3d printing.
Stratsys, quick parts, or any number of smaller outfits can do it.
CF filled nylon 12 works well. I've made replacement parts including fixing a headlight switch for a Ferrari using it.
Any unfilled material will abrade rather quickly. Give an allowance of .005" per side for surface irregularity. Parts can be modeled or printed to-size, but will need to wear in.

Casting aluminum can be tricky. Easier to use zamak or similar casting alloys. Better flow and fewer issues with oxides. Can be melted over a space heater like lead too.