As was mentioned above, finding a preceptor is something that often (usually) effort over time. The best option is to build a network of providers who know you and are willing to help you over time, as these folks will often be able to guide you towards not only a preceptor, but a good preceptor. However, since you are behind the curve here, the suggestions above would be a good way to start. Also keep in mind you are now basically cold calling folks, this type of marketing (which is what you are doing) has very high negative response rates. The more personal you can make it the better your chances are. I.e. email gets rejected with the click of a button, doesn't even take a second to do... Think of how fast you delete spam messages, that is basically what you are going to be to the recipients. Phone calls are not much more, they don't know you from any other telemarketer, nope, not taking the call, leave a message for the round file. In person is comparable to door to door salesman, a little bit more difficult to get rid of, but still with a receptionist, probably not very difficult. Expect high rejection rates, you reject marketers all the time, now you are on the other side of the situation.
A couple suggestions. If their is any kind of conference, or other gathering of providers, even if it's not NPs, this is a good place to start. You can go there, talk to people and see if they know of anyone you can contact about this. Get the contact info and the name of who referred you, so when you do try to make contact it's: "so-and-so suggested I call you about my need for a ....". That will get a much better response than "Can you help me...". A second option might be to contact your hospital or other facility you work at, they likely have someone who coordinates educational opportunities. I.e. someone who works with the schools to coordinate the placement of students in clinical settings. Talk to that person, and see if they have contacts in other facilities. For example, the person who does this for my local hospital has to coordinate placement with some doctors offices as well (the MD students spend time in ER, Hospitalist, and two local clinics not owned by the hospital), so they might give you the right person to talk to at a couple clinics who could help you with placement.
Finally, whenever talking to someone and being declined, always ask if they know of someone or place that might be able to help you and thank them for their time.