Booking and appointment option – how to add extra fields to listing inquiry form

I know that this is not available for now as premuimpress option for directory. I am looking for a way to add this so any suggestion with external plugin is welcome.

Here is what I would need :
– option to modify the premiumpress listing send message form
– add extra fields to send message form, we can add a calendar and time slots so that visitors can choose a date and time while sending message to listing vendor