Sylvia Weinblatt Mazurki, the widow of character actor Mike Mazurki and a former agent and casting director, died Oct. 18 in Los Angeles following a lengthy illness. She was 81.Mazurki began her career at Universal Studios in the casting department and was a well known agent for many years. Mike Mazurki died in 1990. She is survived by two step-daughters, Michelle and Mannette, a sister, two nephews and a niece. Donations in her name may be made to John Wayne Cancer Institute, 2200 Santa Monica Blvd., Santa Monica, CA 90404.