Tip: Honda parts fisches almost always list the diameter and length.
For example...looks like your back where the Rops would mount if you had a 700-4, so a look at RMATV shows it to be a 10mm width by 20mm long. Unfortunately, it doesn't give the pitch, but I bet there aren't that many choices there. BTW, the part number is 95701-10020-00. Perhaps one of the sites do list the pitch.
This isn't THE answer, but it will at least get you in the neighborhood.