I don't know, I think you should do it yourself and use your own ideas and fantasies. Because the story is going to be good if you write about your own experiences and feelings.
You could take some real events from your life and change them so they fit to your fantasy. You could look into other writers stories and take some ideas from them. They have really good stories on
asstr.org and
literotica.com or on
cmnf.coccozella.com. I like Les's (from cmnf.coccozella)stories, he/she is a good writer. The Bet and Kim and Jen are good stories. Those pictures by Blzr is not bad too.
You could read those and then write your own stories.