So far I have been unsuccessful at finding a solution to this. Either creating the option or just being able to sell the eBooks at all.
General developer forum
Presumably you've looked at and rejected solutions like Smashwords or BookBaby. You could advertise the book, cover, content and reviews in one course and then provide a link to a paid course from where the book could be downloaded. Less than ideal I appreciate.
Failing that I think you might have to fall back on a custom solution.