The (Honda or aftermarket-copy) bag rails are not going to be shown in the OE parts diagrams.
It's possible the bolt referred to is the same size as what he needs, but only possible.
The correct bolt is listed in the above PDF Honda bag rail 2-page instruction sheet (1st page), but it's not easy to see which is the exact one needed from the schematic. Is it #8 or #10?
#10, 6mm x 12mm long Flange Hex Bolt