string harmonics with cue notes

[Orm Finnendahl]

Hi,

 I often need to notate harmonics for strings and like to indicate the
resulting pitch as a small parenthesized notehead above the fingered
pitch.

Is there an easier way than the bloated example below?

\version "2.19.5"

{
  <<
    {
      < a' \harmonic >1 ^\markup { "sul D" }
    } \\ {
      \override ParenthesesItem.padding = #0.2
      \override ParenthesesItem.font-size = #1
      \once \override Stem.transparent = ##t
      \teeny \parenthesize \tweak X-offset #0.5  a''4
    }
  >>
}

It'd be probably much nicer to be able to define some expression which
draws a centered, parenthesized notehead above some noteevent with the
pitch given as an argument.

--
Orm