How to make dropdown menus in the widget area from values collected from ACF in a custom post type

I have a site that is for a publisher. I have made a custom post type that is call "publication". As you might guess it holds all the publications. :slight_smile:
I have used ACF to collect an wide assortment of information on each publication to display on the product page.
I need to create 2 drop down select menus that appear on the top of all the pages. One that will display all the titles of the publications in the "publication " type (that's the regular title field not and ACF field) and another drop down that lists all the ISBN numbers for all the publications. The ISBN # is in a ACF repeater field that is attached to each publication page. specs_repeater > isbn

And the items need to be listed alphabetically.

The overall goal is to have drop-downs that build and sort themselves as new publications are added.

Suggestions would be greatly appreciated!
Thanks.

Sandra