The plastic tube is called Polyamid and made by Cohline in Germany.
If in fact the leak is from the tube I should have the correct stuff for you.
The key is the heavy wall thickness to prevent expansion of the line or what is called fuel surging.
If you email me I will send you whatever length you want. Don't know the price but its cheap.
Lots of threads on this board on how to assemble it using your old fittings.
Len at Autosportengineering dot com