A well-equipped automotive machine shop can weld material onto the shaft and regrind it if you can't locate another shaft. The process is called "submerged arc welding" and it requires a special MIG wire welding machine. At one time, a Federal-Mogul main bearing set # 648M was available all the way down to .060" undersize in .010" increments, but they might be very difficult to find. Another 216 main bearing set is listed under part # 484M with 10, 20, 30 and 40 undersizes. I am not sure which set would be correct for your engine.