I have used a small piece of aluminum with a slot for my pliers and mouth opener doohickey.  I have made ones for several of the canoes I have used.  Most of them get screwed into the bottom of a thwart so there is no binding.  This one is mounted differently.
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I have a string going between them so I am less likely to lose them. The short piece of bungee gets looped over the handle of the pliers for portages.
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I have been using variations of this setup for over 10 years and like it.