Changing half-diminished symbol size

[Lib Lists]

I'd like to change the size of the half-diminished chord symbol, but I
cannot find a way to do it.

\version "2.25.5"
\chords {
  \set majorSevenSymbol = \markup { \override #'(thickness . 2)
\triangle  ##f  "7" }
 c4:maj7  a:min7.5-
  }

I'm aware there's not a halfDimishedSymbol, but I cannot find a way to
reconstruct the half-diminished symbol as a markup (similarly as the
\triangle in the example above). Any suggestions?

Thank you in advance!