You can apply for ISBN number from the National Library of your country. (beingauthor.com)
What I don't get (as my previous book was published through a publisher) is if I am allowed to do sell my own book and give away a flip book version when it is also being sold through amazon, and whether the solution is that I should I use my own ISBN number for all versions of the book, or a different one for my free download book? (jamesaltucher.com)
Today I followed a link provided by David Gaughran to a website run by Bowker (the exclusive provider of ISBN numbers in the U.S.). (blairmacgregorbooks.com)