That hose is Just to close off the injector return passage on the last injector in the line. At the other end of the injector string you will see a hose that goes back to the fuel tank. It is a hose with a braided cover. Go ask any volkswagon dealer for a couple of inches of it and find a tight fitting short machine screw to seal one end. They get old and they rot and start to leak and semi vulcanise on sometimes so you might have to cut up one side carefully to remove any part of it that remains on the nipple. It is known as injector return line hose material. You will notice the same material running between all the injectors. You could also get a piece of it off an old mercedes or volkswagon diesel if it still seemed good as well. Auto wrecker might give it to you even. Remember it is not expensive to buy new.