Nice effort by the OP. There's many handlebar bottle mounts on the market priced under $10 to a high of $20.

Here's a DIY simple mount I've done that saves handlebar space and prevents marring. You can bolt any standard 2 hole cage to it.

The stainless bracket is removed from a Minoura quick mount handlebar type. The original stem clamp bolt is replaced with a longer shank bolt. An aluminum spacer is placed in the stem recess. Show and tell pics;