Help with Perfect Bound Booklet Function

Does anyone know of a plugin that allows more signature options for the perfect bound booklet function?

Our book signatures are often 5 sheet (20), 6 sheet (24), or other unusual sheet counts besides 1, 2, 3, 4, or 8 - the only options InDesign gives out of the box.  In order to get around this I am having to print individual signatures to PDF using the saddle stitch option and then combine the sections into a single PDF for printing.  This works fine for the end product, but its extremely time consuming for large books with lots of sections. 

I would really love a way to tell InDesign to export a perfect-bound book with creep using ANY signature number, even if it can only be ones divisible by 4.