I know this is not the answer you were after. But when I got the hoses made up for my conversion I asked if they could identify the fittings at the engine end. The answer from the bloke was "some funny automotive fitting - no idea". Therefore I am pretty sure that its not a common fitting.
New 200tdi hoses with the fittings are less than £20 each online - can you get one modified to put a BSP compression fitting on the steel part either end, retaining the correct fittings and you can then make a hose up to fit between them?
Cheers. Ric