I totally agree that onlyfans, etc., is not the right place to find models for stories.
But, it totally depends on which kind of models you are looking for. There are several websites/galleries with girls who are modelling (also in a girl-next-door-style). When you search for "models" then you will find them. ...and, searching for them is fun too. Just act as if you would search for models for an event in real life... But, for some galleries you have to pay. But, if writing stories is your hobby, then dont hesitate to spend some bucks for this.