I'm sure you've seen Freight Baggage's Road Soda...but what about a double?
The Velcro'd straps wrap around the head tube and pouches so you can cinch 'em down if you're running bottles--or if you're riding on cobblestone.
I couldn't find my thin foam, so I sandwiched some fleece between the Cordura and oxford nylon...for insulation.
This doesn't come off as fast as Freight's, and it'd be awkward to use as a standalone koozie...but really, who uses a koozie? Ha.
See also Blue Lug's version (of the Road Soda, not the Double Trouble).
More people have got to be making these...but I couldn't find 'em...
See also Epic Designs and Carousel Design Works for other crazy bags you can strap onto yer bike.