Need a schleifer

[Steven McDougall]

I need a schleifer.
They appear, for example in Bach BWV 117b measure 3 and BWV 998 measure 21.
I've been piecing them together from a prall and slur, like this

\version "2.10.25"

\relative c''
{
  a4 
     \once \override Slur #'extra-offset = #'(  1.0  . -0.25 )
     \grace { \hideNotes \stemDown a16^([ bes] \unHideNotes }
     \once \override Script #'extra-offset = #'( -3.50 . -2.70 )
     d4) \prall 
}

\layout { ragged-right = ##t }