Does that gear drive a chain? It looks like it from the shape of the teeth.

That was likely made from Nylon, which is a lot tougher than ABS and PLA (what most printers use for material), so I would pick Nylon or a metal for a suitable replacement.

Recreating that in CAD wouldn't be too tough. I would go with Alumide from Shapeways. http://www.shapeways.com/materials/metallic-plastic?li=nav Either that or steel. More expensive, but more durable.

SLS and extrusion methods are two very different ways to print. SLS printers cost 10's or 100's of thousands of dollars and extrusions styles are a lot cheaper. Extrusion melts layers of material on top of other layers. SLS uses a laser to sinter (fuse) powders of that material together. The biggest differences are the standard surface finishes, SLS being much better, and that extrusion prints are very weak in the direction of the layers.

Shapeways does SLS, the other linked store looks like an extrusion style makerbot printer. Pinball Life and Mezel Mods do extrusion based printing as well, which is most of the reason why they don't do anything for me as far as wanting them.