My girlfriend said that, if I find a girl who was okay with it, she and the other girl would blow me at the same time. How should I go about finding the other girl?

Obviously, I really, really, really want this to happen. When me and my SO were talking about fantasies, I mentioned that being blown by two girls at the same time was my absolute top one. She said that she would be okay with it, but that I would have to find the girl because it would be too awkward to ask one of her friends.

So, sexxit, I'm coming to you on my knees (ha). How should I go about finding this other girl? Should I ask one of my female friends? An ex-hookup, go to a party and see who's there? As for information about me and my SO, we're both HS Seniors, both 17, have a very active sex life, and have been dating 6 months.