If I could find the replacement ball bearings to put in the mast bearing housing I would try and put the old housing back together. Classic Industries has the 67 specific column rebuild kit that comes with a bag of replacement balls but it costs about $170 and I don’t need the other bits
included.
It isn't much more than a glorified bicycle bearing. Is there a full service bicycle shop in your town? Might read like a wild goose chase but I know others have found the solution there. Those may have been different models though.