Is mdfind a Windows executable? Is there a standalone version that I might be able to use on the rare occasions I need to fight with somebody's Windows box?
mdfind is a built-in with macOS. It's similar to find (should be on your *nix system if you have one) which can be installed with Cygwin on Windows. On Windows, you'd use Powershell and Get-ChildItem (I don't think it's case sensitive, but I don't use PS much).
mdfind is the command line interface to macos "Spotlight", which is the global file index. So it can do things like full text search in addition to matching metadata values or size bigger than X.
I don't know windows well enough to know the equivalent. But I think there is an index on windows, and powershell may be able to poke at it.