For a small stocking-stuffer gift or something that kids can afford to get for a parent, look for dry bags. They come in a wide variety of sizes and materials and prices that range from about $10 on up. Most paddlers are only going out for short day trips, so a few small dry bags that can hold keys, wallet, cell phone, and snacks are very useful. For more serious paddlers going out in cooler weather or on colder waters, a slightly larger dry bag can be used to carry extra dry clothing to change into in case of a capsize, or just to carry some extra layers like hats, gloves, sweater and rain gear.
Most dry bags use a roll-top closure system with a buckle to hold the bag closed after the opening has been rolled over a few times. This is an excellent method for sealing a dry bag and probably works better than more gimmicky methods. If there are any seams in the bag, make sure that they are sealed with a good waterproof seam tape or you may get water leaking in through the seams.
Clear bags or at least ones with some clear windows can make it easier to find what you are looking for without having to unpack everything you have stashed in your dry bags. I like to use a red dry bag to hold my first aid kit.
Since a well-used bag will eventually wear out, and most paddlers like to have several bags of assorted sizes, there is very little chance that your gift won’t be very much appreciated and used.