chantal and mike
my 4700 must be equipped differently than yours.
it has a juntion box at the base of the left hand side of the drivers seat. it has about 8 or 10 LED's (light emmiting diodes) on it. it is for the remote start etc.
the over head console has six switches in it for cargo/spot lamps and the pto.
i thought all internationals were equipped this way.
my thought was that you could tap into any of the key on accessories to power a battery solenoid.
back to square one.
you need to find a circuit that becomes hot with the key to close a relay.
then you could use the bosch relay that frank posted.