I can't show you a photo because the boats down at the yard, but I use two 35mm film canisters to protect my two Garmin cable connectors. If you make a cable sized hole in the lids, then a slit from the hole to the edge, you can attach the lids permanently to the cables, just behind the connectors, with some waterproof sealant. (I used Sikaflex).
When your GPS is not in use, the cannisters are clipped on to the lids protecting the connectors. Remove the cannisters to connect the GPS and stick 'em in a pocket until you next remove your GPS. They're cheap, replaceable and effective.
I agree they're probably unecessary, but it makes me feel as if I'm doing the right thing!