This is similar to the ones in my dads car, except the ones in his car look more like the pictures, and were a black spring steel.

I remember because my hands were small, so he asked me to get it off. like this
[ATTACH=full]98518[/ATTACH]
This one is closer

Volvo

This band clamp comes big enough for the barrell I _think_. 48mm

I realize that these have two pinchers on one side, but im not convinced the original didnt either.
As for the caps, they look like bicycle or other nozzle caps. Which would be plastic and screw on to just about anything.