Is flexible water jacketed exhaust hose a thing? My motor is so close to being done, I really don’t want to have to fabricate my own exhaust (I can if I have too, I have the tools and piping to do it). Dry portion of my Gil manifolds is 4.5 inches (I think) and with the wet portion it’s 5 inches. Is there hose I can just hook on or am I going to have to fab up a piece of stainless tubing to extend from the manifold before connecting to exhaust hose and finally dumping out the tips?

Without even looking, I Highly doubt something like you are asking for has ever been made. Your dry exhaust pipe will more than likely be 3.5", your riser will dictate this. Have your extension welded to the inner riser pipe and weld some simple, small stand-off/ spacers on the other end to keep the annulus open when your 4" exhaust hose goes over it - this will keep the water flowing around and keep the rubber hose from resting on the hot inner exhaust pipe.