Adding ARIAL or HELVETICA FONTS in KOBO AURA HD

Hi all,
I recently had to regenerate my Kobo Aura HD... after a long day I now have it again with all my books.
However opening the book I was reading I discovered that the font I was used to (arial - helvetica) is no more present in the list. May be it is something related to the update but I like to read in that font.
Is there any way to add it to my kobo?
I've asked to Kobo support but they told that this is not a standard and supported feature.

Any suggestions?
Thank you !
Chiara