Hear is a useful idea I found on the YACF forum

Somnolent said:

charging of Garmins from a dynamo while on the move is problematic even in the dry.
Nothing that can’t be overcome mitigated with a little ingenuity.
Been running my Etrex (HCx) from the Luxos USB offtake for a couple of years now.
I’ve fettled a 6″ cable with sugru at either end to make something tolerably water-resistant, and which minimizes mechanical loads/vibration on the USB socket.
Keep meaning to remove the cable when it rains, close up the covers and run on battery for the duration of the precipitation, but somehow I always seem to forget and its still going strong.

From the Sugru website:

Sugru sticks to wood, metal, glass, as well as most plastics and fabrics.
It bonds much stronger than contact adhesives, adhesive strips or silicone sealants.
Once it’s cured, Sugru is waterproof, just like other rubbers.
You can use it in the shower, the sink or even the sea.
And thanks to Sugru’s heat-resistance, it’s even dishwasher-proof.
Sugru isn’t rigid like other glues – cured Sugru bends like a firm, flexible rubber, so it’s perfect for use on textiles, shoes or even low-current cables.

Consumer Reports says:

What we found. As we expected, a pack doesn’t go very far. Sugru sticks adequately to non-porous surfaces but not as well as a true adhesive. It isn’t as soft as some other silicones once cured, and it’s not especially strong. And while you can compress it without problems, it didn’t handle stretching well.

Bottom line. We wouldn’t use Sugru where failure of the bond could create a safety or health issue. But in cases where filling a gap is essential, a structure requires some reinforcement, or surfaces don’t align well, we found it fun and useful—there are many situations where the usual adhesives wouldn’t apply. Still, we recommend it for non-critical repair tasks.

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