I bought a bunch more of these than I needed, apparently, because there are still 8 of them in the bag. The picture shows three of them so you can see them from 3 separate angles to be sure they will do the job for you. They do not have a set screw, though are thich enough to add one, and the eyepiece is a light fit. That is, the adapter would fall off the eyepiece if you held it up.
$1 each plus shipping