I also own a 2006 x244 2.8jtd. However my vehicle has the black plastic bodied UFI filter, confusingly called a green filter in eLearn. (The UFI plastic bodied filters on the later x250 model are partly green coloured.)
I am not sure that it will help, but I have attached an extract from eLearn for the x244 model depicting the fuel supply components.
Perhaps the queried item is the low pressure relief valve?
Given that our vehicles are now 17 years old, parts supply could be a problem. Especially so for rarely required items.
Coastal Motorhomes have a good reputation as a supplier of parts for older models, and I have used them on two occasions. Otherwise perhaps a vehicle breaker?
For part numbers, inputting your VIN into
ePER , which is available at the top of the page, should help.
Given that I have a similar vehicle, I am curious to learn that you need these parts, in case I need to take preventative action.