Have you tried Past Parts in Bury St Edmunds Suffolk? 01284 750729 or 0843 5155606. Fax01284 756240
web
http://www.pastparts.com
email
restore@pastparts.com
They are specialist in brake parts for classic cars and listed on the BOC website.
I have no connection with the company other than to say that they have always found part, usually in stock, for my Bristol.