Here, 10 to 20 EURO is usuall DAILY sallary. But if you mention nude posing, girls start to talk about thousands. So, no posing for photographers, no money for girls, and it is closed circle...
Prostitutes are usually NOT good idea. There is simple reason. Girls less care (relatively speaking) what they are doing, they are worried what will be KNOWN they are doing. That is, girls easier try to earn money as prostitutes (if theire famillies, friends and like don't know how they earn), than pose nude. If they pose for nude photography/painting/sculpturing, people will see them, and that is problem. It is not matter what is done, but what people know they do. So, prostitutes are often off the limit. Here is like that, and small communities, traditional communities, patriarchal communities, strong religious communities often have that hypocritical moral stand. I wouldn't try prostitutes. Exotic dancers, but serious ones, not ones who use "dance" as cover for prostitution, are better choice than prostitutes, they have been seen nude and that is one thing less to worry for them. Prostitutes hide themselves and they do not want to be seen nude on pictures, double life you know.. Fashion model agencies also are not good choice. Those models put themselves too high, they are not suitable for private work (unless you are Peter Lindberhg or like, but...).
My first choice would be art school, at first models for students, or students themselves. Next, ballet dancers. Then modern dance dancers. Dancers for latino-american dances or waltz or like are less open that ballet dancers, I would not try with them. That is how it is here, and from what George tells I belive it is simillar at his place.
Put small add on information board in those schools or theatres and hope...
One thing. It would be good if you can afford next: Try to go somewhere else, let say Germany or wherever on weekend workshop for nude photography. That way you will get few prints you can show to eventual future models. It is one thing talking about nude photography, it is another thing if you can show example of your work and what are you try to make when ask her to pose. I never was able to afford something like that (not only money, problem here is traveling, we don't get visas easilly), and I would like to do that. Yes. it is not ideal, lots of people are there, you have no time or space to do everything you would like to try, but for start, who knows. Maybe some girl, and even one who reject you in first time would accept your proposition if she can see what is in matter why you need her.
George, I very well know your situation, I am in same situation here. Wait and hope, and don't give up, it is what can be done...