the one i had was held on by the starter motor cover bolts and replaced the cover itself
one hint though - DO NOT mount the starter button on the side of the box - the only place to put it is on the left hand side and should you stall the motor at the lights, you won't be able to just pull the clutch in and hit the starter button and go....no no no...you will have to pull the clutch in, put the gears back in neutral, reach down under the seat, find the starter button, start the motor, hand back to the clutch, pull the clutch in, back into first gear and (finally) off you go - if you don't stall again....
you could ask me how i know this but i'd have to kill you (just like the car drivers behind me at the lights wanted to kill me after i performed the above series of actions)