The indicator fitted to the UK 400/4 was actually the dish type, 303 in that diagram 43145-369-000. It's hard to find but should be easy to reproduce if someone has the skills.
The washer was actually a large diameter thick washer as the washer underneath was rubber to avoid vibration and ringing through the torque arm, as such it needed a washer of the same size so the rubber washer underneath wasn't distorted out of shape. Measure the rubber washer and find a thick large diameter of the same size, see to remember the washer was 8mm internal diameter, whereas the rubber one was bigger as it went over the shoulder on the torque arm bolt.