Dremel or hack saw, length wise, on both sides, then pry it off, or polish the sides, and look for a small ring, which would be a pin, if it was pinned on, and not glued. Is this a German import, or Indian? Yeah a longer tang would be a definite, benefit, as that is what caused it to break in the first place. You can do it yourself, or have a welding shop do it. You can get a couple of vice grips, and clamp at the ricasso? or the area just below the pewter, and set the blade in a coffee can or other container of water with either ice cubes, or dry ice, and weld on an extension on to it. You would have to prep the existing tang and all first. But it is not a big project. You then put the original handle on with some spacers, or put a new one on. Just my thoughts.
Wayne