I believe the only possible way is to either modify the search code, or use one of the filters. I can’t really think of an easy solution, I’m sorry.
You can take a look at some examples in the knowledge base how to parse and modify the results, for example: https://wp-dreams.com/knowledge-base/numbering-the-results/
In that example you have access to the post ID as well with the
variable in the foreach loop.
Then if you know the post ID, you can use wordpress core functions the get custom fields and so on.
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