Answer

If you mean a Ganadhara of Bhagwan Rishabhdev, the commonly mentioned name is Vrishabhasen (also written Rishabhsen). ( jaingpt.org)

Explanation

The word Prajapati is associated with Bhagwan Rishabhdev as a title, not as a Ganadhara name. ( jainworld.jainworld.com)

Spiritual Understanding

Bhagwan Rishabhdev’s chief disciple is remembered for helping establish and organize the Jain order in the early tradition. ( jaingpt.org)

Takeaway

So, if you are looking for a name starting with Pr, that is likely Prajapati as a title of Bhagwan Rishabhdev, but the Ganadhara name is Vrishabhasen / Rishabhsen. ( jainworld.jainworld.com)