There is a lot less to them them meets the eye.
Make a "recoil pad" out of wood, make a mold from it using pourable moldmaking mat'l, then get some 2 part urethane to make the "rubber" part of the pad, and a different hard urethane for the "plate" part of the pad. Probably take a few tries to find the right durometer.
The pads were probably made from a machined metal mold due to the necessity for removable pegs to form the recoil pad holes, but at least some and possibly all of the gooey combs were made by making a rubber mold from an original comb like I outlined above, so there's no reason that couldn't be done for a low volume personal use type situation.
I thought about going down this route to make them for myself when they first became scarce before COVID, but didn't want to blow a few hundred bucks on materials to figure out how to best duplicate them, and then I switched to Microcell pad which is just as effective if not more so at mitigating recoil and is a lot lighter. I do miss the shape of the curved trap gooey pad (the shape was a nice compromise b/w curved, flat, and rocker shapes), but what I found was I'd get a 10/10 mount about 90% of the time, and a 1/10 mount 10% of the time, causing me to have to dismount and remount, whereas with the Microcell I get a 9/10 or 10/10 mount nearly 100% of the time and very rarely have to take the gun down and remount. I did cover the face of the Microcell with some RTV silicone for grip, as the factory finish is very slick, and like a sheet of ice if it gets any moisture on it. Plus the Microcell is 1/2 to 1/3 the cost of what a Gooey was, and a gooey was good for 1 to MAYBE 1.5 seasons, whereas I'm still on the 1st Microcell I ever installed with no signs of replacement being necessary.