Coxy would be a good choice, actually, he'd be my preferred choice, because I know the quality of his work.
(And he's a bloody good bloke too...I like the man; but don't tell him I said that!)
But it's not really a major undertaking from what I've sussed from the Gearvendor's site; two to three hours work, and we do have competent engineers locally who would be perfectly capable of this sort of thing.
So I think we'll opt to get it done at Pete Moller's place in New Plymouth.