RE: CN2220A where to get one??
The mainshaft thrust bearings are of not much consequence on helis in the 30 to 50 class range, as the specs of these radial bearings are such that they can easily handle the weights and g-forces of these smaller and lighter helis. They are of more consequence on the much heavier 90 and gasser sized helis.
I have, and have had over the years, a number of 30 and 50 sized helis, and their initial mainshaft bearings all lasted well over 400, rather demanding, 3D flights. What usually will damage these bearings is NOT the in flight thrust loads, but the extreme side forces they have to deal with in a crash, when the mainblades make contact with terra firma....specially if under full power, as opposed to in an auto.