1- Posting ads online, then if contacted trying to approach the subject in a professional manner. Non-pro/fetish girls are never going to be overly optimistic about this type of shoot, so depends on how you frame it and the money of course. The pro-models will be more straightforward and have standard rates but you still have to display professionalism.
2- Finding women in bars, cafes, parks, university campuses etc... More tricky and again, a lot will depend on the way you come off.