Delta Unidrill help

I began working on an old Unidrill I got several years ago and found the worm gear that raises the head has long since gone away. Go to Delta or is there a better source? 1.5" long, approx 4 tpi, .5"shaft, guessing original dia of 1 1/8 to 1 3/16". Thanks for the help. Respectfully, Ron Moore
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