I have an abacus you could borrow, not much use but looks uber retro cool man.
bahahahaha
I would wait until you actually see where you are going first mate, then make a decision once you ascertain what the environment is like and as chirone said if you really need one?
cheers bullet
PS yes they are all expensive mate so choose wisely. If you dont need one, money saved.
bullet1968
"A Darkness at Sethanon", a book I aspire to model some of the charcters and scenes