Good news is that I've found a 3D printer and can pursue my project of making translucent eye cups. I just need to figure out the best way to model and slice them now 🙂
Perhaps 3D printing an opaque inner layer then coating that with a translucent or transparent layer (printed, dipped, or just melted and drizzled on)? You need the light-guide outer coating to extend inside the eyecup mounting holes, to gather some light. Just alternatives to try, for comparison purposes...