It is at Australian Amazon,
https://www.amazon.com.au/Gray-House...dp/B01JZAKPF0/ , as well as other Amazons (
https://www.amazon.co.uk/Gray-House-...dp/B01JZAKPF0/ ,
https://www.amazon.ca/Gray-House-Mar...dp/B01JZAKPF0/ ,
https://www.amazon.de/Gray-House-Mar...dp/B01JZAKPF0/ etc.). I don't think you can buy the ebook anywhere else, because it is Amazon's own imprint, but I can send out a .mobi or a .epub to any club member.