How to access purchased Books after moving Countries?

I moved from the US to Taiwan several years ago. I would like to reread a book i previously purchased in ibooks, but it does not show as something I have purchased even though it is available to purchase in English. I can’t change my region on my account because I have an Apple Music subscription. Is there truly no way for me to access an ebook that I have already purchased?

[Re-Titled by Moderator]