I have this mount (image below) and am wondering what is a better fastening setup.

I currently use standard nut + bolt + washers. Does the job but requires a pair of tools -- one to turn the bolt and one to hold the nut in place -- whereas I travel with a single multi-tool.

One idea is to use some kind of wing nut / knob instead of a plain nut. But maybe there is a better way. Is there? the picture shows an interesting finishing washer. Threading the fork with a properly sized tap would be better than a rear facing nut.