I saw these classic metal water bottles at Hiroshi's shop, C Speed, the other day. Beautiful, light and strong. There is a cork under the cap and, of course, the cap when unscrewed and inverted will serve as a cup. They would go great on a restored classic bike ... though they are not inexpensive, and the shiny mirror-like finish (right side) costs extra. Still, they should last a long, long time.
Hiroshi tells me that they are made using the Japanese "herabori" technique, kind of like cutting away metal with a spoon, I guess on a metal lathe.