3D FlipBook - Customize shortcode HTML for Lightbox trigger

Hi. Purchased the wordpress version of this plugin on Code Canyon. Everything works great, thank you! But I'm trying to keep our website accessible and the shortcode inserts a div with an onclick function rather than a button or link tag. Can you point me to a way to customize the HTML inserted for the lightbox trigger? I've taken a look through the code but didn't find anything obvious. I did see a Lightbox CSS Class setting, but it only seems to be available when editing an individual flipbook rather than in the global settings.

This is the call I'm currently making in a template (I'm creating and storing the flipbooks dynamically when I save categories): do_shortcode('[real3dflipbook id="'.$category->term_id.'" mode="lightbox" class="reader-btn" thumb=""]')

And here is an example of a page where that shortcode lives: https://magazine.napavalley.wine/issues/issue-no-11/

It works fine, but as the div is not a focusable element, I'd like to change the HTML output for the trigger to a button instead. Is this possible?