How To Search Gallery Images By Caption?

I am using avada theme but i dont think this is theme specific. I have to upload about 500 images to about 5 different galleries. Each image in a gallery has a unique caption (fred, john etc etc). I want to be able to search to be able to find a specific image via its caption. I cannot find any plugin or way to do this,

Is there a way to achieve what i need. My understanding is that i could create portfolio posts and the post title will be picked up in search BUT to setup 500 portfolio posts is too much work, unless im missing something??

Many thanks