I cannot stand the silly prices people ask for what I know is a cheap item to buy wholesale and rubber filler pipe is one of them ( I used to collect and deliver it for a black country rubber company) . I may be wrong but I reckon any flexible good quality fuel pipe will do the job for a tank end filler when it is fitted correctly. I mean come on it is only filler pipe and people have been using it for years when making kit cars etc so why can't we use something like the stuff in the link below - or do we have to pay vw tax to make it right and safe? http://www.cbsonline.co.uk/product/ULTRA_FLEXIBLE_FUEL_FILLER_HOSE_57mm_(2_1|4")_FFF57 Just asking like!
Only thing I can think of is there is a bit(flap?) at the top of the filler which the filler cap screw onto holding the filler next to the vehicle. That flexi hose does not seem to have it.
Think its down to the proverbial " custom and practice". Look how long that horrible single braided hose has stuck around.