Ever go to any conventions or festivals? Plenty of casual hookups happen there.

The hippie/burner festivals where you're camping out are great. They're often clothing-optional, sex-positive, and kink-friendly (if you're into that).

Found this one. Likely more to be found, it's definitely ot exclusive to the U.S.

https://mmm.kiezburn.org/

Darn, someone doesn't skip leg day.