The 300's swingarm has riv-nuts for the hugger mounting screws, but you can just drill and tap (M6x1.0) the 250 swingarm.
The hugger itself is
36014-0555 and the two mounting screws are
92154-0918. Just for the sake of completion, the two regular mounting shoulder screws for the left side are
92151-1703, if you don't have them for some reason.