filler tube

If you can't find something ready-made to do the job, I would be inclined to make it from mild steel (eg. exhaust pipe) and get it galvanised. The filler area tends to collect condensation which will cause rust. This will inevitably find its way into the tank and cause problems. Not sure what the 'legal' situation is but would check with the tank manufacturer before going ahead.
Cheers, Cruiser.

The Exhaust tube will do the job,but if you are joining it to something else be sure to get the right type of hose.

Royce,
I purchased steel wire reinforced rubber hose (oil and fuel safe) from the Hose Shed to reposition my filler. Because it is reinforced it does not kink around corners.

Graham