Unplug the Toro's power cord from the wall.
Use a screwdriver to loosen the screw on the underside of the Power Curve's control panel, beneath where the handle key would normally be inserted. Take out the screw.
Twist the lever arm mechanism to the right to the "On" position with a pair of pliers. Leave it in this position. This will keep the handle unlocked until a new key can be obtained.
Replace the plastic panel piece on the bottom and replace the retaining screw with the screwdriver.