That's a part that's going to be very hard to find. Back the, it was a very hard to use and 'finicky' part to keep in alignment, so most users just tossed it out. As I recall (from seeing Dad's) it was just a piece of sheet metal with some sort of pivoting three-sided channel fastened to it. 1950 was pretty much 'pre-plastic' days, so the actual guard was metal, and it blocked the view of the blade. The 'splitter' part of it was much thinner than the blade kerf, so it would've been of marginal use, too.
Unless you're restoring the saw for a static display or a museum piece, I'd suggest looking into something like a Shark guard, or something similar.