That's my thought.... but I live in cyprus and 'accuracy' such as requesting a perfect right angle on the fence, is a bit of a stretch here. There's a local guy 'Iron Horse George' who's very good, but again, I don't know how perfect he could make it.For that age of a nailer - very doubtful that you will find a supplier. Maybe that is why you have a wood fence now instead of metal. A suggestion is to go to a metal manufacturing shop, I'm sure they can build whatever you want.
Have you considered a new or good used modern style Vnailer?