I have always felt it to be better to alter the existing handle, rather than change it. The handle is installed by copper induction brazing at the factory. It will be reinstalled by sivler soldering using an oxy-acetylene torch in all likelihood. A jig can be used to insure proper alignment. The handle saddle and the rear of the bolt body, where the cocking cam is located, will be subject to red heat, and cooled. This may well affect the hardness of the cocking cam.
By converting the knob into a threaded shank, an extended or oversized knob can be added, with the use of heat.
There are also those who TIG weld replacement handles in place. This is reported to work well.