Been down this path a couple of times and you are right, the metal is the (expensive) issue. Some years ago my friend and ‘smith called me for some help with a 20ga Ithaca that had come in missing its forend. It was a family heirloom that had been inherited and the non-shooting couple wanted it for their mantel. I happened to know where one for that model had been (and turned out, still was) but it was missing the metal. Since they only wanted it for looks, it was a fairly inexpensive modification to fit the wood to the barrels with a nice looking cover plate and they went away happy for relatively short money. The other time I needed a forend I had the metal.
I hope someone here has a similar gun and can help you with the measurements.