Clothes pins can still work, you just have to loosen the springs a little. Take a clothespin apart, and bent the metal springs with vises and pliers so that it doesn't close all the way. Another thing you could do is put something in between the jaws of the clothespin to keep it from closing all the way. You know, kind of prop it open. I use a broken paintbrush handle on one set i use on myself, and a slim twig for the other set I have for my nipples for long-term wear. See if tht makes the sensation a littleless intense. With a prop the jaws will still close around the flesh but won't grip as tightly.
I hope this helps!