/diy/ - Do It Yourself

i gotta fabricate a couple plastic parts. Or at least approximate them for a prototype.

they're too big to get 3d printed at a reasonable price. I'd like to machine my own molds for injection molding. I live near a TechShops and I took classes on it, but i wont be willing to pay the monthly fee for a while, and I dont want to put this all off and lose momentum.

It's this and another thats basically the same but inverted to fit around the lip, and no disc in the middle.
Is there an economical and fast solution that might produce better results than just slicing up PVC pipe and gluing it all together.