The 3/8"-16 bolt for the Smallrig ARRI Top Handle I had was either missing the retaining clip or Smallrig doesn't supply one. I lost the bolt and wanted one that I can hand tighten. I used a 3/8"-16 carriage bolt and cut to length and made this knob to slip over the threads and tighten down the handle. Print with outside to inside layers first so that it maintains dimensional accuracy.

I also designed a spacer between the handle and camera cage, you can vary the thickness in the slicer based on what you need, I used TPU for it.