Hmmm
Penka is supercute and modern
Aspen?
Penelopa is a Slavic version of
Penelope, I read that somewhere
Pence is an interesting medieval-quirk sort of choice
Pepin, or
Pippin; male names technically, but in this day and age who cares.
On the other hand you could also use it for any name you want - I once read a non-fiction book about a woman whose real name was
Susan or something, but her parents called her
Penny when the nurse said she was "as pretty as a shiny new penny".
I actually really love the idea of Pence and
Penka. I would think those so adorable.