It doesn’t matter where or at what level they work: look for people whose lives revolve around the challenge you want to tackle. If you can’t find them directly, it may be a good idea to ask around among department heads or with partner organisations, volunteer organisations etc. Quite often the same names will come up. That’s when you know these are the people you need.
And if your challenge is in line with the areas of concern of these people, it will take no effort at all to make them enthusiastic about it. Once you have succeeded in triggering people in their passion, you will notice that nothing can stop them. However, they may sometimes head in the wrong direction. It’s the responsibility of the process supervisor to keep everything on the right track and to anticipate any problems.