I don't remember anywhere in my manual or any other that gives me bumper dimensions.
COULD you MAKE one of those bumpers work, either with a little heat and some bending or maybe some special brackets? Yes. Would it be worth it? No, because 99% of the bumpers available for those bikes are available for the 660. If you're getting a heck of a deal on one or free then just sell it and put it towards the right bumper.