R2-D2 Holoprojector Lens

thingiverse

This is a printable lens for the holoprojectors if you don't want to use something like a marble or acrylic ball. I found that painting it black and giving it a couple of coats of gloss made it look quite good (although technically it should be clear). Depending on your printer, it might be necessary to sand the print or resize the model very slightly to get it to fit right.