M2
You can use a lanyard ring from an M3 size flashlight on the M2.The rings rotation will be limited by the M2 clip. The lanyard is attached to the ring.
10X Dominator
On the 10X, threaded a (color of your choice) paracord through one of the holes on the side of the lamphead.Thread two cordlocks onto the paracord and tie the two ends togather.
You can also use any of the Surefire lanyards for the 10X by removing the clip, taking the cord apart and proceeding as above to thread the lanyard through the hole on the 10X head.