Hey @kharris, that's a great question. If I were in that boat, I would probably go blog hunting. Find people who write about the topic, converse with them on their blog, and get a feel for if this is the kind of person you are looking for. I imagine it would be time consuming. But I bet you could meet really great people this way.
If by chance you do think they would be interested, then shoot them a personal invite. If they decline, then I would ask if they happen to know anyone who might be. That way you can say, "So-and-so recommended I contact you..." to the people on that list.
Does that help?
If others have a better approach, I would love to hear it.