The Team Orion stock motor for the Micro RS4 is a FK-180SH. It differs from the motor you are decribing only in its intended voltage range. I picked one up locally for $13. As soon as my wire arrives, I will be rewinding the armature, going for some serious top speed.
Here is the datasheet on that motor:
http://www.mabuchi-motor.co.jp/cgi-b...AT_ID=fk_180sh
...and here is the datasheet for the motors used in the Norelco beard trimmer. I'd be very concerned about those high current draws on the stock electronics, and it also sounds like the brushes will not hold up under the 4.8-6V range like they will in the FK-180SH.
http://www.mabuchi-motor.co.jp/cgi-b..._ID=ff_180phsh