It should be past the patent age now. Even if it was within the patent time frame, it's hard to enforce a patent violation if its not a production product. For AGD, it wouldn't be worth it for a small run. They would have to make a large production run for it to be worth while. They would have to produce the X-valve front but cut like a classic at the back.
Someone would have to measure and cut one on a mill for it to be done, I suspect. As a project it would be nice, but not profitable unless someone was willing to pay way too much for it. The regulator is less complicated than the front section is why the back section had so many aftermarket copies made.
Except for the Automag in front, its usually the man behind the equipment that counts.