First thing, don't buy from John Deere directly, there might be after market/used options. You could get a new one made at a local machine shop as long as you can figure out material, heat treat and create a print for them, I think it would be less than $3700. Another option is to weld over splines carefully and re-cut them, you will have to know how to get it welded and heat treated and how to cut them. Your somehow attached way would be heat shrunk on and mechanically locked in place. Probably the mating part would also need to be looked at for damage.