There are a lot of ways..LinkedIn can help greatly and even for that matter freelance sites like Elance, Guru, etc if you are tight on budget.
Specialist outsourcing company can be of great help but finding them can become tricky at times. I happen to use TechCusp.com for my company and although I was not very sure of performance, I was pleasantly surprise by the results shown by them in the last 3 months and that too at a decent cost.
If you need any help, feel free to reach out to me.

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.

You want a good one, go to AngelList or Hacker News / Jobs.
If not contact on Twitter my friend @kikischirr who is an expert on marketing. She wrote a book on Product Hunt that went viral.

Check out CloudPeeps! Sort of like Clarity but specifically for social media + community managers: https://www.cloudpeeps.com