I believe Eric has a plug-in that will work, and there's also a tutorial (for sale) on how to draw gears in Corel or similar. However, I'm hesitating on those, since I don't know if they allow a very specific tooth shape. Apparently modern self-lubricating gears have an elegant, non-intuitive tooth shape that makes for efficient engagement, low-friction force transferral, and disengagement. I have a feeling Photoshop will work, but it's a matter of getting all the teeth to be identical (and correctly spaced) that precludes a tracing operation (or any non-mathematical solution).