Hi Peter,

Here are several workarounds for you. Open BIAB with the style ZZJAZZ (the simplest all midi style) and then mute everything but the piano. You'll get variations on the sound you want using:

C7#5#9 which gives the same variations as C#9b13 and C7alt.

With the choice, above, you'll hear both #9 and b9. The most consistent results, with #9 and little variation is given by Gb13/C

A nice alternative is Dbmmaj7/C

These can be put together for added color.