This box for your Omnifixo "3rd Hand" has a magnetic closure and space for the clamps to be stored. But, rather than let the clamps rattle around inside, I mounted clevis pins (3"long, ¼"diameter) inside. The pins don't do anything more than provide a metal surface for the clamps to magnetically attach to.
6mmx3mm magnets (qty 4) are used to attach the lid.
The author marked this model as their own original creation.