Hello Ian,
Do you mean the top shaft gear which is quite common to strip underneath the top cover ? you can get most spares from www.sewing-machine-parts.co.uk, if you intendo to replace the gears yourself and they are the top gears which I think they are, you will need to retime the machine afterwards completely, if you can't get the gears from above try www.sewingonline.co.uk.
Any problems fitting the gears or retiming let me know, e-mail me.
Ken
drivewithken@blueyonder.co.uk, August 2007