What is the easiest way to get our northeast asia tour operator company listed on the large, global tour inventory directories?

We run an educational/adventure tour company that goes to northeast asia (including N. Korea) and need to know the easiest and most efficient method to get listed on the best directories in order to get in front of the most appropriate travel agents and agencies. In many ways, we are also "non-profit", because we believe in the humanitarian engagement side of our model. This means we sometimes run tours at cost in order to accomplish our educational and engagement goals, helping folks develop organic and lasting connections across political and cultural boundaries. If you feel you have the ability to give us expert guidance that will help us expedite this process efficiently, please share your initial thoughts, and we can do a phone call.