Here's a low buck, or possibly no buck option, depending on what you already have on hand for tools and materials. I've seen some car and truck projects where people have made shifter, E-brake and transfer case handle boots out of leather, denim or neoprene. Something like that might work for the flexible center part. The narrow end can be sewn with a bungee, zipper or velcro strip to close it up around the hoses, cables and wires.
As far as the outer trim pieces, what about making your own out of a sheet of aluminum (easy to work with) and a hole saw? A large diameter hole saw for the outer diameter and a smaller one for the center. A drill press table you can clamp the material down to would be helpful to keep the holes aligned with each other, but isn't required though. You can also just clamp the material in a vise and drill the outer hole first. Then clamp the cut out piece back into the vise and use the same center pilot hole to align the smaller hole saw to cut out the inner hole. You could make it pretty much any size as long as you have the hole saws to match the OD and ID you want. After it's cut out and the edges cleaned up, polish it up until you get the shiny finish you want. Since it's going on a boat, some clear coat paint would help it to maintain the shiny look a lot longer after it's polished.
