I have looked for this general style in really thin pins, no luck. I think you mentioned once you had seen them down to about 1/8" ? Where?This style pin works really well in a lot of situations prone to pin knock out.
My 3 pt hitch on the B tractor came with some cotter pins right where you need to frequently pull them out to adjust lower links. Couldn't even unbend the legs once to pull the pin, and had to cut it out. Replaced with hair pin, but something sturdier would be better.