Sam, is it the MY1016 scooter motor? If so, I've just taken delivery of a new one for Onyx that has the sprocket still attached. I don't use it (I weld a Technobots one on instead) so if it looks like it will fit, it's yours.

It has got 11 teeth though, not sure how that plays into your axe ratio. The scooter motor currently in Onyx also came with a sprocket that might have been 9-tooth (certainly was double-D). Can't remember if I held on to that one but I'll have a look tomorrow morning and let you know.

Here are a couple of pics of the 11-tooth sprocket:

P1020814.jpg

P1020818.jpg