A few years ago, Paula posted about the Kayak Kaboose, a device that is essentially a floating extra cargo hatch for your kayak. Attached to the back of your kayak, the kaboose floats behind in carrying your extra gear.
Now, another company has come up with something similar called The Kayak Kaddy. This looks to be a more compact version, and, as seen in the video below, can be towed easily behind a sit-on-top or even a SUP. If you have to take everything with you when you go kayaking, this piece of gear might be just what you need.