Trying to find a odd shaped fan blade
If the blade is a flat panel, no surface contour, you could either duplicate it yourself or find a wood shop or makerspace with members who might assist. It would be a simple matter to drop a panel into a laser cutter, cnc router, jig saw, band saw, so many options if you can identify the material from which it is constructed. Jasen's suggestion of replacing all three is a good one, as well. 3 mm or 6 mm plywood would be quite strong for this application and not particularly heavy. Our fans have veneer over particle board, cheap and heavier than ply.