While you are conducting your search, there are some procedures that will aid you. You can always spend the cash on a "paid" people search site or even hire your own Private Investigator. You will find that the Web is often times the best way to conduct your investigations.
Many sites will give you the people search for free but want you to pay for the data it returns.
A search on a free people search engine will help you find out if you want to spend money on the remaing results. If you do not recieve any results then you can always move on to the next site.
Be patient and use all the resources available on the Net. There are litterly thousands of people search engines ready for you to use. Stick with it and put in some elbow grease and you will suceed at finding your subject.