Is there enough room on the inside of the eyelets for the fender mount if you use a panhead M5 bolt and a washer or two to clear the hub and spokes? Or, would the plastic fender thingy rub on the hub?
I had a Surly rack years ago, I mounted it on the outside of the fork and mounted my fender inside, but the fender I used did not have a plastic fitting like you cite. And my fork was a LHT fork from 2004 which might have different specifications.
P clips would probably work. My Thorn brand bikes have the fender mounts up higher above the dropout, that is not a problem at all. I assume you are talking about the rubber and metal ones like these, but this example is probably the wrong size.
https://www.homedepot.com/p/Gardner-...1600/202875644