My BMG bowden adapter broke so I made a new one that takes standard pressure fittings. This should be much more robust than the crap stock one.
I have included 2 different kinds, an M6 or an M10 depending on what you have laying around. The M10 should let you push the bowden all the way through. The M6 you need to cut a small piece of bowden that is 15mm long. Stick that through on the inside towards the gears.
Print so that the tube is flat, ie: the hole needs to be parallel to the build plate. Please see the picture.
edit: for some reason thingiverse stopped showing the picture and i can't fix it. please see the print orientation here: https://i.imgur.com/pFv2dHQ.jpg