Do you mean the union with two male threads? It is not listed as a spare part but I'm sure Garrett sells it. On older engines it was listed as a spare part. I don't know why it's not in the parts catalog for ALH.
VW# 028 145 786 is listed for European TDI engines with similar engines with threads m10x1/m14x1.5. My best guess is that it will fit, try checking the threads yourself and see if it'll fit but use at your own risk. I have no idea why it's in the European part catalog for the same engine and not in the North American part catalog. Please post a follow up if it works, thanks.
Also, moved to the mk4 section since this is more technical than a parts wanted ad.