Expert in Public Relations, facebook, youtube, twitter, instagram, etc.
I don't want to be a wise guy, but I think the Internet would be a great place to start; particularly social media. What ever your product or service is I am sure that it resides in an industry, and I am willing to wager that industry has thought leaders. I would start seeking out thought leaders in your space and come up with a short list that have a reasonable social media following. The clout of the people on your list should coincide with your ability to compensate them. The benefit of using established thought leaders is that they are already tied into the community that you are trying to win over, and your thought leader probably already has the trust of your prospective customers. I cannot however stress enough the importance of due diligence prior to reaching out to a prospective thought leader, because you are trusting this person with your brand to a degree.