Harbor Trunk Bag Black. Stay dry and keep moving with the Manhattan Portage Harbor Collection. The Harbor Trunk bag was specially designed for urban bike riders. Made using a special coated poly/nylon blend fabric, welded seams, and locking waterproof zippers, this bag is 100% waterproof in both fabric and construction. Wearable two ways: either on a rear rack of a bicycle or cross body as a shoulder bag; wet weather