CHICAGO (UPI) — Police today sought a youth who bought medi cal dressings for cuts on his face about the time a woman's body was found brutally slashed in a church doorway. More than 50 detectives and ficemen worked to find the killer of Gertrude Lewandowski, 40, an unemployed office worker slain in an unexplained attack at Blessed Sacrament Roman Catho lic Church. Hunted was a youth who bought bandages and gauze at a drug store near the church about the time Miss Lewandowski’s body was found stabbed 80 times beside a holy water font late Wednesday.