Although, you have requested for noun. I'd suggest an adjective Eminent.
According to Oxford Dictionary
(of a person) famous and respected within a particular sphere.
Your Example: They met at a ritzy lounge frequented by
Eminent people.
I will also request you to check all the example sentences provided on Oxford Dictionary. Few of them are as follows:
1 . "It was also patronized by eminent scientists, corporates and intellectuals."
Here, patronized can be used as follows:
Frequent (a shop, restaurant, or other establishment) as a customer.
"restaurants and bars regularly patronized by the stars were often crowded with paparazzi."
2 . "To find answers this programme gathered together a group of eminent people from a variety of backgrounds."