This one is for the upright-bar folks.
The Minoura BH-60 adapter could be a lot more elegant, but it works an absolute treat and doesn't damage anything. It also hangs the midpoint of the bottle at the centerline of the bar - not above it - which is one of the reasons I chose it over the more lithe BH-95X (and, for that matter, over all the other aluminum adapters today that place the cage too high).
The VO Retro Cage makes the whole thing work.
-Kurt