Voltbike urban 2l thermos mount

I have a [voltbike urban](http://www.voltbike.ca/voltbike-urban.html). I want to carry a 2l thermos with me, but its too large for the saddlebag.
The cross-bar is rectangular.

This part sits on the cross bar, and the thermos sits on it and then I use a velcro strap.
I described it more in my [blog](https://blog.donbowman.ca/2018/06/04/of-electric-bikes-and-cargo-3d-printers-and-thermos/)