What I would do, which may be as useful, is to make up a short converter cable to go from whatever external starting power connector you have, to the 3-pin plug I posted above. That could be done within 1kg.
Peter wrote:
That could be done within 1kg.
That plug alone weighs from 0.7 to 1.1 kg, depending on the manufacturer.
You would need the other half (which can be found quite bare)
plus a plug to go into your existing aircraft socket. Plus some 10cm of wires.
How about having this little guy in the airplane at all times? Weighs less than 1 kg.