We've created this Forum Thread with some workarounds and advice to assist you in publishing you ebook.
Question on custom ISBNs and eBook formats
I already have my own ISBNs and I'm looking to publish in ebook format and sell to multiple outlets. But I'm confused on one point. How is it possible that a Lulu project with a single ISBN can be distributed to channels that can't (or shouldn't) reuse the same ISBN?
From the video tutorials I've seen, it looks like for a new project I can: 1) provide my own ISBN, and then 2) distribute to different outlines (for example, EPUB edition for iBooks and MOBI for Kindle). But I don't get how that can work.