i have a steering stem hanging on my wall of shame just like that, it happens when someone forgets to install the cotter pin and the castle nut starts to work off, allowing the taper to flop around in the stems flag.
unfortunately, it's welded to the stem and you'll need a new/used stem.
dualstroke might have one for sale in his partout he just listed yesterday, reply to his thread for him to message you, then you can reply back to work out details, unless you can find one locally ?