Edited...
Found the flat black paint at Autozone.
Was curious and started searching (again) for a vent gauge mount - and I finally found one!
The reason I went with the KOSO was that was the only option that I could find that would work and look good in the vehicle. With that being said, if someone wanted to start with an easier boost gauge setup, they might start with this:
https://www.ebay.com/itm/Air-Vent-Ga...-/324156279582