This is the stock spur gear for the RS4 RTR 3 (single speed).
http://www3.towerhobbies.com/cgi-bin...?&I=LXBSZ5&P=7
I think it may be the solution to the one way bearing hurdle.. I bought a 2 speed for my RS4 but never got around to installing it so I'm not totally sure where the bearing is. If you need to replace the two outer bearings I'll find the part number for ya.I think you can re-use the shaft and drive cups with that spur gear. But if you want me to find the part numbers for them I'll post them tomorrow.
If you want some more torque, the MT spur gear has the same dimensions.. aside from the number of teeth of course.
http://www3.towerhobbies.com/cgi-bin...?&I=LXTB39&P=7