parenthesized grace note

[plutek]

anyone have a method for putting parentheses around a grace note (other
than building the whole thing with \markup)?
specifically, i wish to have a parenthesized small notehead beside the
main note of a trill, to indicate the trill note.

yes, i have seen the discussion about placing an accidental above the
trill sign; that is not what i'm looking for.

thanks!

-p