I’ve done some casting which I mentioned not long ago.
I can’t tell if your part has a chance of being made in two halves or if it is going to need to be a complex cast. If you can get away with a two-part mold then you have a lot more options, including lower temperature metals like zinc or even bismuth-tin which is very easy to work with. If you need a complex shape then you will have to resort to burning out PLA (or wax or foam). I’ve never tried that method, although I have burned out fire ants…