The primary source is the report of the State Canvassing Board, available at the Wisconsin Historical Society in Madison. The results can also be found in the 1964 Wisconsin Blue Book, on page 760, but the Blue Book excludes the write-in votes.
Source for Popular Vote data: Wisconsin Board of State Canvassers, Statement of Board of State Canvassers for United States Senator General Election - 1962 (Madison, 1962)