I scoured google and found a good one from some overseas hilux forum I think, then headed to Jaycar and got a few bits and made it for $4.45 and 20 mins of my time...
1x 12v (5-16v) piezo buzzer;
1x 1N4007 diode; and
about 10cm of wire.
Lights (+) > diode (the end without the stripe) > buzzer (+) > ignition (+)
So I soldered the stripe end of the diode to the + of the buzzer then added a bit of wire to the other end of the diode.
I then opened the corner of the dash (L series) to get to the light switch and connected the wire I soldered to the diode onto the red-with-white-stripe connection which showed to only activate with lights on.
Then I needed to find a wire that was off without the key but on when it was at the first stop (like the wire that turns on the clock on the radio) - there was a stray connector just behind the lights which happened to have just the thing I was looking for so I hacked a crimp connector to fit then attached the wire and tested it a few times, then put eleccy tape over the buzzer cos its so damn loud.
It works and I'm proud
