On the Links page of my UnblinkingEye.Com site I have links to several model forums, including FigureModels.Org, FineArtFolios.Com, One Model Place, and Web Models. These are excellent resources for finding models. http://unblinkingeye.com/Links/links.html
Models who are just breaking into the business will often pose in return for photographs. This is called TFP--time for prints. Approaching people you don't know is problematic at best, so the above forums are the recommended place to start.
You should also consider creating a page with a standing request for models that gives your location, e-mail address, and the terms you offer. I have such a page at http://unblinkingeye.com/Links/Model/model.html. Be sure to add the proper description and key word tags so search engines can index the page, then send the URL to all the major search engines. It may take time, but eventually you will begin to receive responses. It also helps to live in a college or university town.