Hello I was heading down the path to have an adjustable comb installed on my Webley but once the local gun smith pulled the recoil pad he quickly realized it couldn’t be done due the lightening of the stock the gun maker performed. They removed a ton (well that might be an exaggeration!) of material from the inside of the stock and as a result there wasn’t enough material to support the hardware.
That said there seems to be quite a few reputable companies that will modify your stock, you would just need to send it to them. I agree you don’t want someone who says I think I can do it and makes a mess of a beautiful piece of walnut and now your left replacing a stock.
I ended up buying a Beretta 686E with a factory adjustable comb so I guess I fixed the problem, but can’t send you to anyone just maybe have a look in the stock and see if you think there is enough material. I can send you a pic of mine with measurements if that would be any help