I don't know what the rig is in the background, but my gut says it's a hart-parr. my dad has one in the shed, its from 1926 and is an 18-32 model, i think, i've only ever seen two other ones in person and they were 16-30 models if i remember correctly. although, I can't say i've seen one with a hood, or a rear mounted fuel tank like that. all three that i have seen have a round fuel tank mounted between the radiator and the engine.
I don't have any banjo bolts, but CC jersey is correct, you can make them with a regular bolt and a drill, then you just need the copper sealing washers.