The power button is not sold separate from the upper case. One could possibly be salvaged from a watre damaged upper case (I just looked at one and it would need to be torn apart to get to it. However, the power button is rarely the cause for a machine not starting. It's much more likely that the ribbon cable is not connected correctly to the logic board. Have you opened the machine or spilled any liquid in it. Please give a more exacting list of your symptoms and the history of the machine.