Sew-Classic.com has new cover plates. I recommend you buy some bobbins there as well. I've had bad experiences with new Singer class 66 bobbins having too narrow of a rim to fit vintage bobbin winders. Sew-Classic sells quality bobbins.
Also check your bobbin winder tires before you order. It's common for them to break down and not work anymore. Sew-Classic has them and they're cheap to replace.
Rodney