Bass clarinet in A

I need to write for a Bass clarinet in A (treble clef). Is there a way to get the right transposition?
As a workaround I tried to use a Bass Horn in A and change the sound in Halion, and it works. But the brackets of the woodwinds gets broken.
Thank you very much in advance
Stefano Rabaglia

You could try a Clarinet in A and have Halion transpose down an octave. Otherwise it will take some XML hackery.

Understanding that a few composers wrote for Bass Clarinet in A (Wagner, Mahler, Ravel, etc.) please know that while a few instruments do exist, the vast majority of A Bass Clarinet parts are played on a B-flat instrument. As a professional orchestral librarian and clarinettist for over 40 years I can tell you that I have never played or even seen one.

So it might behoove you to provide a transposed part in addition to the original.

Thank you very much Craig and rkrentzman.
Different solutions but both are effective.
Stefano