Place "Opus" instead of Instrument Name?

Question

I'm trying to place the opus to the left of a Staff (which is normally the place of the instrument name), like this:

Is there a proper way to place opus in replacement of instrumentName? Something like what we do in \paper{ scoreTitleMarkup = \markup ... }.

The only way I know for now is to set a FAKE instrument name, which seems to be a bad way of layout hacking:

\version "2.24.3"

melody = \relative c'{  c4 d e f   }

\score {
  \new Staff \with{
    instrumentName = "No.1" % IT SHOULD BE OPUS INSTEAD!
  }
  \melody
}

\score {
  \new Staff \with{
    instrumentName = "No.2" % IT SHOULD BE OPUS INSTEAD!
  }
  \melody
}

I tried with the \context setting but it didn't work:

\version "2.24.3"

\layout {
  \context {
    \Staff \with{
      instrumentName = \markup \fromproperty #'header:opus
      % NOT WORKING!
    }
  }
}

melody = \relative c'{  c4 d e f   }

\score {
  \header {
    opus = "No.xxx"
  }
  \new Staff {
    \melody
  }
}