Isn't that the solar powered one? The one used in UNSW tests?
I suggest just getting an older Casio fx82TL which has the exact same functionality and uses a battery or if you really want, the one up from the series that has a sort of 'undo' functionality. I've had my fx82TL since Year 12 and it's still good.
Tandy sells the non solar power version of it. Except, it is the newer model with the circle up the top instead of the two arrows (for the replay function).