Casting your own tail light lens

I'd really love to see how someone can "easy" design a lens like that. Do not forget: It has to fit. It has to look right. It has facets and reflective surfaces inside. It has to have a great surface finish inside and out (most printers create parts with layers and a rough finish). It has to be clear & red & withstand heat/cold/rain. I don't even think there is a suitable resin for this.