Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
Dowty washers are aluminium crush washers with a built in O ring. You can pick them up on eBay. You buy them by ID. Just measure the bolt size.
http://www.yamiya750.com/index.php?main_page=product_info&cPath=21_66&products_id=1974£3.50 for the washers... and of course £20.00 for postage...