[readingglasses]

There is one solution if you can live with the device not being simply in its shell. You could just connect a battery pack over usb and run it with a dead battery inside, perhaps. Depending on the circuit paths.
But the battery will eventually leak on the other components and it's not a cool looking solution.
So, I guess this is a "disposable device" after all. Maybe a tech repair shop will have the skills and tools to replace it with ease, though.