1990 Caravan (148,000) which still runs and rides great. My granddaughter is getting too big (48 lbs) for the 5 point (baby) harness and now requires a shoulder belt by Maryland law. When shoulder belts first came out there were kits which allowed you to add a shoulder belt to an existing lap belt. Any idea where I can get either a add-on kit or a complete shoulder belt whcih I can install for the back seats?