We have fender skirts in various widths but it comes down to how wide you need. We have 2-1/2 inch wide by 61 inch like with # PX52-188 which is a very common size.
To see other options we carry I attached a link to see them all. view full answer...
The Trailer Wheel Center Cap # 319EZ may be a little too big if you measured right at 3-1/8" for your hub bore. Since this is a fairly precise measurement I recommend taking it again and possibly use a digital caliper like part # PTW80157 if you have one handy to make sure it fits.
I do not advise grinding the hub bore out at all as that could compromise the integrity of your hub. view full answer...