I think the "oversized" means that they are for 1 1/8th diameter bars. Ex. the Pro Taper bars.
You could get sleeves made, but that gets kid of sketchy when it come to handlebars.
PS- I have a set of Z1000 risers that will fit those bars.
Look here: http://www.customfighters.com/forums/showthread.php?t=37954