V band flange for downpipe - what is it?

I like making things myself so I want to make my own downpipe rather than just buying one off the shelf.

So first thing I need is a V band flange on the end of my downpipe that will mate up with the turbo's V band flange... and apparently its not just your average V band. For a start its got a recess in it for some kind of gasket to sit in. Trouble is I can't find any kind of name for this style of V band and even looking through entire catalogs of parts from various clamp manufacturers, can't find anything similar.

I spoke to a shop here in the UK that has just released a downpipe for this car and they said they couldn't find anything either so had to get one custom made. They'll sell me one of theirs but for a pretty high price, and it won't be here for a few weeks, so I'm keen to try find an alternative solution. I find it hard to believe all these people making downpipes for this car as well as M140i etc are having to measure the stock flange and then get a custom one made by a machine shop.

So yeah, bit of a long shot, but anyone got any ideas or suggestions where to look for this?