If you want to make your own plastic parts (HP28 battery door, other battery doors or trays, or even your own calculator), take a look at
The price is $500. The claimed resolution is a fraction of a millimeter.
Is this like Polaroid (film) or inkjet printers (the ink): are they planning to make their money on the plastic? They charge $43 for 2 pounds of ABS filament - I have no idea whether that's a good price or not (or how much "stuff" that will make).
(PS I have no association with this company.)