Good luck trying to find one. It seems that the only racks that work with the factory sissy bar come only from Yamaha. The only other one made to work with the factory sissy bars are no longer made. I was lucky enough to find one from a generous member of another vstar forum.
I absolutely agree with YamaEd on this. It is really tough to get luggage racks for the factory sissy bar and Yamaha sells it at a very high price. My brother was lucky enough he stumbled across an online website that sold all kinds of pièces moto for Yamaha bikes. The rates were also very low and the quality of product is nice too. He bought luggage racks and some other accessories from this site. You should take a look at it to try out your luck.
Anyone have a large sissy bar bag you're looking to unload? Brand unimportant but quality and condition should be good. Let me know what you've got and what you're thinking as far as price is concerned.
Thanks and ride safe.