The Azerite Bar does not exist in game yet, because no gear uses it. What I had to do in my ElvUI plugin is check if an Azerite item is found.
Lua Code:
local azeriteItemLocation = C_AzeriteItem.FindActiveAzeriteItem()
if azeriteItemLocation then
-- do stuff
end
You can create your status bar now, give it starting text, color it, whatever. You'll have to Hide() it until the expansion drops, and any event scripts will have to check as I have above. The code you see is found inside my event handler that updates the bar.