If you're after nuts and bolts of any size, then
Bolts and Industrial Supplies is worth a look.
If you're like me and don't have your own transport, then a good mail order place for this sort of thing is invaluable.
I've just ordered some 1.6mm metric screws, your local Bunnings DEFINITELY doesn't stock those!
And for the electronic side of ATMs,, check out
Sparkfun. Lots of components, microcontrollers, etc.
Ocean Controls in Melbourne also have an interesting range of 'stuff' including small stepper motors.