I wish I had one to throw an A-rig with.
I can build you one if you have a higher ratio. I have a set or two of the gears I think.
The Main Gear, The Pinion Gear, The Drag pressure plate, The drags and the yoke has to be changed to make one.
But I will caution you. They are SLOW but I had not thought of A Rigs. That would be ideal.