In the 4x18650 department, i suggest you have a look at the Q8 project which will essentially bring us a SRK on steroids (6000 lumen) for $40. But it won’t be available before a few month at least. A simple white plastic cup will make a decent diffuser. No usb charging though.
Did you consider one of those 10/20/50W flood projector that run off the AC? They are rather cheap and quite handy.