Include section numbers in header/footer

I currently use $Pagegrouptitle and $Pagegroupparenttitle to reference the parts and chapters of my book.

Since they are there for user navigation, and my book is organized with hierarchically-numbered streams, I would like to be able to put those numbers in the header:

<$n#part>. <$PageGroupTitle>
<$n#chapter>. <$PageGroupParentTitle>

I am currently investigating pdfpages and latex to be able to insert those after compiling, but that is difficult.
I am open to suggestions about exporting to other formats, but most export options involve hand-tweaking after export, which is not a workable solution for me.

Thanks,
-alec