Brushless Gimbal Design and Parts Questions

I am working on building a DIY brushless gimbal and i am looking for some information about bearings and motor connections. I am using 5106-150t motors with no extending shaft. I have noticed some designs use a motor cage for this type of motor then add a small connector to the face of the motor that creates effectively a shift extention. This then extends out through a bearing thus putting most of the load on the bearing and not the motor. I am trying to find out the name of the part that extends the shaft. It looks like an adapter of some sort that screws into the face of the motor. I am also trying to find a source for purchasing it. I am only looking for 3 or 4 of them since this is a personal build. Any help would be great!