Have you tried the links on the DOC website? Have a look here:
http://www.duttonownersclub.co.uk/car_spar...nes_&_gearboxes under "Fuel systems". If you mention that's where you found their advert then you may or may not be entitled to a discount. Technically you're probably supposed to be a member to take advantage of such offers but at the end of the day if you're not and they offer you a discount you'd be a fool to say no!
Apologies if you've already tried them and they're out of stock or can't help or a bit too dear or whatever.
You converting an auto to manual or something?