Ashleymadison.com be very careful about posting profiles with pictures online. Remember these sites all sell your profile pictures to others to use to drive business.. Nothing worse than your friend, boss, or husband getting a picture of you in his gmail promoting a sex hook up site!
If its with his/her permission I'd recommend www.alt.com or www.adultfriendfinder.com and just be honest about the situation and what you are looking for... Both of those sites I have used in the past and both worked great!
2 words "Russian Roulette". I.e. it's not something you can predict. I would 1st try work although it is frowned upon. Next, see if your friends or co-workers know any one. If you really want to be discrete, try the internet. You have to realize that you might not be able to find someone close, though.
a free site called "plenty of fish."