I did a bit of searching and found these shaft collars. Rudland was the only company I found. They make this single, warp-around plastic collar which is the least expensive and doesn't mark up the L-rod or pad. They offer split rings and other materials (metals). The part number — CL-7-P is the 7/16" plastic one that works with all my L-rods. $25 (Amazon) for a pack of four isn't cheap, but they really do the job.
I do have to use a flat blade screw driver to spread them open to slip on some of the heavily knurled rods.
I position the split in the collar to center on the rear center of the pad. You could scribe an alignment mark on the pad, but eyeballing it works well for me.