If you can buy a replica like the one in your posted photo cheap, that sort of makes it easier to do a real duplication of the Krag sight. You would still need the mill, and a barreled action is probably too much like a gun to keep you honest.
The other way would be to purchase the krag replica and measure how much needs to be milled off the bottom. Then modify the sight at work. There are several ways to generate the radius needed to solder the base to the barrel. It would not be as strong as the armory method but probably good enough.
The attached photo shows an instruction manual and a sample Weaver mount that I made.
In case you have not found the photo of the Krag barrel with the sight removed   (You need to Login

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