I've been using a homemade gadget for years that was given to me by one of my dad's life-long friends. To my knowledge, it was his own invention, but I don't know for sure. Regardless, he crafted all kinds of neat accessories for hunting and fishing.
It's just two alligator clips joined by a short piece of strong bead chain screwed onto the end of either clip. The length of bead chain is approximately one and one-half to two inches. One of the metal clips is bare for good grip, and the other has heat-shrink tubing covering the jaws to protect tippet material.
Both clips are attached to either the edge of my vest, shirt placket, or waders. When it's time to change flies, I place the tippet end of my leader in the jaws covered with heat-shrink tubing while the other clip stays attached to my apparel, and this frees up both hands to do other things while the tippet is securely held in place directly in front of me. It might sound somewhat hokey, but it works amazingly well for its intended purpose.
The next time you're at the dentist, ask if you can have one of those bead chain/clips they use to hold the splatter bib around your neck. Shorten the chain, add some heat-shrink tubing to one of the alligator clips, and rock on.
Edited to add: A picture (or two) is worth a thousand words. Oh, the bead chain is probably three inches long.
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