This unit has a custom front panel header, you would need to replace the panel with the switch and everything else that it contains. This would be working on the assumption that the switch is intermittently defective and not the computer. You could try searching ebay for parts. Alternatively you could jury-rig some kind of external switch, but you would need to discopnnect the exisiting header and find the proper pinout diagram for the custom header so that you could attach it to the right pins.