The pitman arm is located at the bottom of the steering box, and that is usually a factory only part. In all the years that I have worked on cars, I can never recall ever finding a pitman arm except at the dealership. On the other hand, if you have your terms mixed up, then what you might be looking for is the idler arm. This is a replaceable part that is commonly found in the auto parts stores. In fact, I can only remember needing to replace one pitman arm ever. That was on a collision damaged car. I have done an Internet search for a pitman arm for your application, however, I cannot find one listed on any of the sites that I have checked. I did check for a replacement steering box, and found a AC Delco unit available. I then checked to see what other vehicles interchange with this box, and the results are listed below. Possibly you might find one at a salvage yard. Bring your old one along for comparison purposes. Usually if the box is the same, so is the pitman arm.. Good luck..
AMERICAN MOTORS(1980 - 1987)BUICK(1980 - 1996)CADILLAC(1980 - 1992)CHEVROLET(1980 - 2003)GMC(1980 - 2003)OLDSMOBILE(1980 - 1992)PONTIAC(1980 - 1992)