Copal shutters never come from the manufacturer with an aperture scale because the aperture scale depends on the lens. The lens manufacturer produces the aperture scale. I suggest contacting Schneider to see if they still have the part, and how much they charge for it.
An alternative would be to have a CLA (Clean, Lube, Adjust) done on the Compur. The Compurs are fine shutters, but with age the oil in any shutter congeals. Your description suggests that nothing is broken on the shutter, so a CLA should bring it to virtually new condition. S.K. Grimes Inc. and other repair places will do this work for much less than the cost of a new shutter.