Hi I agree with Steve and Gareth on both options, can you specify what has failed as if its a pipe its either repairable or substituted with a different material with a similar bore, if you look at it I wouldn't mind betting your system is exactly the same as the A4/A5/A6 I think its a safe bet as VAGs love of globalisation means one part fits a load of other models, I to am a cabbie and I know exactly where you are coming from, I feel for you I really do, no car is like someone has cut your throat financially, I have come across this none in the country for your vehicle CR@P loads of times as with my engine mounts, ended up buying FEBI units which also fitted the A4 with a CNHA engine, oh no I was told by the main stealer they wont last, 70k later says no difference. If you get in a jam just get the adblue mapped out until you can get the parts its a lot cheaper than being off the road for six months.
Steve.