I started with a stock Ultrafire WF-501B and took that whole thing apart.
I removed the LED pcb and replaced it with a custom pcb with the NVSU233A mounted it. I could probably have reused the original PCB with some hacking, but I didn't want to short out anything.
I was originally worried about the driver board giving too much power, but it have been working well with the stock driver circuit. I will look into a custom current source later.
I have compared the UV output to my other UV flashlights, and this one now outputs the most brightest UV light. At night I can light up any florescent object over 25 feet away, or more.
Shining on white paper is almost blinding. the light looks more white compared with the other UV flashlights. I think those are closer to 395nm, vs the 365nm of this one. The lower wavelength helps spot more stuff as well.