i built one a couple yrs ago for a customer, aluminum, looks like a cooler cage you see on boats, with rod holders. i custom fit it to bolt to existing brackets on the jet ski. it came out real good, but i didn't charge near enough. didn't realize how much work was in it. might be able to adapt a pier cart or luggage rack to do the job, it would be much cheaper than a custom job.
es le bon ton roulet