You can email the folks at Grady to get the specs/dimensions on the tanks. Then just give them to whomever you choose to be your tank builder. Several in the NJ are to choose from. The two that immediately come to mind are Patriot Marine and Atlantic Coastal Welding (speedytanks.com I believe).
I got the new tank for my 227 from Sunrise Marine Tanks in Fl. Even with shipping to MD, Tony was the cheapest by a few hundred. The tank itself isn't the prettiest I've seen, but it will definitely get the job done. Highly recommended!