Washers , part number 40- 470, quantity 2 off, plate 9 in the parts book, item 8 in the illustration.
", and I don't see washers in the factory Spares manual.)
The screw seat can be dressed flat with an old screw cut short and a dab of grinding paste. A fibre washer can be used , if al or cu isnt handy, fit a stack of washers to a 1/4 bolt, sandwich with a nut, chuck the bolt in a power drill, file them down to suit, poor boy lathe. most folk have a power drill and a file.