[GeoffR]

You might consider writing to the publisher and asking them if they can make the books you want available in your country. This has worked for me on a few occasions, especially with US publishers.

I think if the publisher is not sure about their rights to sell in a small market like New Zealand they figure it is not worth the effort to check when the book might not even sell one copy, or US publishers might assume that a UK publisher would have exclusive rights for New Zealand. But it seems an email from someone wanting to buy the book can be enough to get them to check, and when they do check sometimes they find they do have the rights after all.

Edit: The same can work for self-published books that are exclusive to Amazon: Write to the author and ask if they can make them available at another retailer, sometimes they will temporarily while there is no promotion on at Amazon that requires the book to be exclusive.