From what I've heard, not all Isetta's were equipped with steering dampers. Fortunately for me, both my Isetta's did have steering dampers. If you don't have a steering damper, and are wanting to add one, hopefully this photo will give you an idea of the placement of the brackets on the frame and tie rod. My replacement steering damper came from a VW parts dealer called CIP1. the part number is VWC-211-425-021-A. They are currently priced at 35.95.
Original Boge GmbH steering damper. Boge part number ATP 22-165-01