The Anniversary Edition with the preface read by the author — me! — is exclusively available on Gumroad as a DRM-free mp3 and mp4 download.
The 11-hour audiobook version of Zero to Sold: How to Start, Run, and Sell a Bootstrapped Business is available on these platforms:
The audiobook has been submitted to many other platforms. This site will be updated once the audiobook appears in new stores.