Just ordered two from ebay, the seller said they're new, for less than $30 USD shipped, it's a nice bargain.
Typical: 10 rpm @ 6V
Shaft: 3mm dia. shaft with fix screw notch
Size: 10mm x 24mm ( no included shaft) length
Reversible by changing polarity
Mounting: M1.5 x 2 screw
All metal gears
For the relatively slow speed, they will be good for motorized focusing, or autoguiding. I shall try to locate two suitable shaft coupler, to connect these 3mm shaft to the 6mm shaft of my TG-SP II.
Mounting would probably be a simple plastic plate, the controller box will need to design and implement, I hope this box will allow manual guiding by pressing buttons, or by an autoguiding port through a computer.