Are we talking Norfolk Island? You may be facing a challenge there. We had a member from there some years back, but it seemed he did most of his buying online. The tourism website is very much web 1.0, and the yellow pages not much better, but they do list a couple of possibilities. There may be film available at Photopress International by the airport, or Camerahouse in Burnt Pine, but that is just guesswork on my part.
Of course, if you're in Norfolk UK, your prospects should be much better.