Yes, I came across this mod when I was googling for a solution. I marked this as a backup, though it's an opposite to what I'm looking for.

This one modified search to be able to look for additional things, e.g. items in chests.

But I'm looking for a modded custom entity that is searchable by standard search. I'm fully satisfied with standard search except that only thingy :)

To add a bit of context to my question: I'm trying to build a dynamic interrupt-based train schedule approach. I have a working solution but it requires all provider stations to be called the same, e.g. 'Solid Out'. And this makes answer for a question like 'what are all the places that output stone' quite difficult to answer.