Neutral safety switch - lists for approx. $50; located on left side of transmission. Secured with two 10 mm head bolts. Need to disconnect power harness and gear shift rod prior to removing switch. Doing it yourself takes about an hour, clearance is a little tight.
Before you condemm the switch - check the condition of the gear shifter rod bushings. Fatigued or missing bushings will result in excessive freeplay in the shifter rod's position and miscoordination between the in-car gear lever selector's indicated position and the neutral safety switch lever's actual position. The bushings (115 992 03 10) are less than a $1 each but are a pain to install, due to limited clearance.