I was looking through my material stash for tube to make the air tank, and this old sink trap was just the right diameter!
I cut off a chunk and trued the ends- sanding off the gunk on it- and drilled for the rivets.
Top and bottom caps were turned from brass, and I made up a little condensate vent for the bottom.
I tested the paint on a spare chunk to see that paint would stick to the chrome- seems fine, no less scratch resistant than brass.
In Kozo's design this holds the battery for the headlight, but I'm planning to use an LED with a coin cell, so is just decorative.