Nice idea, but its a kinetic "wind-up" (nop pun intended) device, the GPS mouse needs a constant 12V supply. As you might know the Tom-Tom GPS mouse takes a few minutes to "settle down" and locate the satellites, a temporary charging device like this wouldnt really be suitable.
Great little device though, especially for emergencies.
In theory all you'd need is a small 12VDC battery. Obviously the Amphere/Hour capacity/ and physical size of the battery would give you a longer operating time. Anyone happen to know the actual "running" current demand of the GPS Mouse?