In the US and the UK, you can buy “What’s Yours is Mine” direct from the publisher, OR Books. Here is the book’s home page. UK copies are printed in the UK.
In Canada, the book is published through Between The Lines. Here is the book’s page on the BTL site.
In Germany, the book is published as Deins ist Meins by Verlag Antje Kunstmann. Here is the book’s page on the publisher’s site.