We currently do not offer them as replacement parts. Technical Service does have a very limited supply of replacement tips.
Most standard replacement bit tips are expected to be used in a magnetic bit holder that will clip in to the driver. The Circuit Alert screwdrivers use bits that have a spring loaded ball bearing in them. We do this because with the Circuit Alert function of the screwdriver, the magnetic field from the magnet in the driver could cause false readings. If standard replacement tips are used, they will fall out of the screwdriver.
Gardner Bender FAQ 