The Honda helmet holder #ZZ50310 specs seemed close to what would fit my 2004 Sporty, so I took a chance and ordered two. It's metric, 8mm to replace either lever pivot. My 5/16" pivot pin is only .0035" larger; difference is so slight you can't feel it. Perfect fit, with a 6mm nut locktight-ed on the bottom end.
And if you want matching, keyed-alike mini locks, you can go to the Wal-Mart hardware department and buy a set of 2 or 4 Master locks. My set of 4 is labeled 121Q. They require filing or grinding the corners of the lock bodies for clearance. Take off just enough plastic/aluminum to slip over the knob. If you take off too much you will expose the hollow insides of the body. You can see the modified lock profile in my pix,
http://i240.photobucket.com/albums/ff187/Jimwright_2007/IMG_1085.jpg