O1
The key in getting o1 visa is a good lawyer who is experienced in this issue. 5-10 letters are needed, from different sources (different countries if possible). If you have many publications/ presentations and work in the area crucial to US economy or defence you will have a very good chance. There are many websites describing this visa. Do a few searches, call a few lawyers. They often evaluate your case without fees and if you get a lot of positive answers go ahead and pick one.
Good luck