This stainless steel watch band tool will help you get those little spring bars in and out of your watch casing. If you just shot a spring bar across the room and lost it in the carpet, you can buy more here.
“Works well enough for the task, though the insertion tools screw in loosely and have to be retightend often to avoid it falling out. Fortunatley, they provided two spares for when it does fall out and get lost.”