Threesome advice!

JazzieBearxo💕💕 • 30. always looking for new friends. hit me up💕💕 twitter/ig: jazziebearxo
okay, so i just read a post about it and offered some advice, but now i'm hoping for some. 
my fiancé and i have discussed having a threesome and have agreed to do it since it's a fantasy for both of us. i told him that i would choose the girl, and he would pick the guy, just to make it a little more comfortable. he chose a friend of his that he's absolutely okay with and isn't bothered by the thought of adding him into the fun. i had an acquaintance of mine chosen, but she bailed out before it could happen because she began to get serious with a guy she was seeing (totally not an issue. things happen). BUT since then, i haven't really been able to figure out how i would pick someone else, she was pretty much perfect for the job. i saw someone mention that it's best if it's a stranger, but i'm not sure. i think i'd prefer someone i kinda knew and trusted a little bit. 
i just don't know how to bring it up to anyone i do know, or how to even bring it up to a stranger. all i know is that i just want my threesome to happen because i'm greedy lol
suggestions? 😁