Heres a video to give a good rough idea what is required. Only difference is instead of making a v spring you would only make the one side. Might be a better option to see if you can find a similar spring (possibly the 1891 Argentine Mausers use the same style, I don't know just a possibility) and modify it to work.
Gunsmithing - British Side-by-Side Shotguns How to Make New Leaf Springs - YouTube