</font><font color="blue" class="small">( It wouldn't be hard for a machine shop to build one. )</font>
Lets see.. Off the top of my head.. front and back plate.. 4 bearings, and some sort of retainers, two shafts, with a 1:1 gearset. Could even be spur gears. Throw a pto adapter on each side, and tack some walls to it and fill with oil.
Hard way to go about it.. but deffinately doable.
Soundguy