Leading zero on keynote legend by sheet

Hi muggles, here’s one I’m struggling with regarding keynotes. I’m quite sure this is a dead end but still…Maybe some python script can help- :fairy:

I need a “keynote by sheet” legend (not my cup of tea but those are major oders…) I’m looking to add a leading zero to all 9 first keynotes. I i would have had a “keynote by sheet” legend easy peasy but…

What I’m looking for:

Thank you all :fairy: