I think your question should really read "where do I find girls with sex appeal of 100?" I assume you're familiar with the procedure Carnacien mentioned.
Well, you find them everywhere, you just have to have high enough sweet talking skill; other skills or attributes might ply a role, too. For me, I can find them when going for a city ride, when joining a party, or in a disco... but I'm level 83. Still, this is just getting a contact, you still have to make her your fuckbuddy (this step will probably* cost you a CC or two) and then a hooker (it might turn out he doesn't want to be one, and there's no chance to make her one, she'll be an actress).
*) I'm saying "probably" because you can try to win her over without spending CC, you just have a low chance of success; in my case it's about 20%. If it's hard for you to even get a contact to a maxed out girl, you probably don't want to go this route.
