Hi James
I flew with Air Nelson last April from Nelson to Wellington, and then up to Hamilton, manging to get the jumpseat for the first leg.
I'm not sure how to go about getting it authorised in advance, you could try sending a letter, but not so sure if that would work.
I just wrote a note explaining who I was and asking for the jumpseat, handed it to the flight attendant whilst boarding, who then handed in to the captain, who invited me up front!
It's a bit hit or miss as to whether that'll work, but I think most of the guys wouldn't have a problem with it. It helps if you're one of the first people arriving at the aircraft, that'll give you the best chance.
It might also depend on the weather on the day, if it's pretty bad they might not want anyone else up there, that's the reason I wasn't allowed up front for the second leg.
But definitely ask, the worst they can say is no!
GWidgery