Looking for a very specific type of Alt Text app

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I'm hoping to find an alt text app that will allow me to change the alt text for an exact listing. I've changed up a few of my keywords and it only affects two of my 100+ listings. I have a bunch of images for both listing and routinely change them around so I'm hoping to find an app that will allow me to customize the exact alt text I want and apply it to all of the images on JUST those two listings.

I had a good look through the app store, but quickly became overwhelmed. There are a bunch of different apps, but nothing that seems to do what I want.