If you can find the smaller cable in the length you need locally, cut off a 3/8” section of a 3/8” grade 5 bolt, drill a small hole in it for the cable, then drill it out half way to 1/4” for the barrel end. I would see if I could find a ball end cable first or grind the barrel so it’s round if you can’t find the ball end but I guess if you could do that you wouldn’t be here asking for help.