You will need a driver to boost the voltage up to the LED’s working range. Right now Zebralight has one. Expect some in the future but right now they don’t exist for hobbyist.
This is the second topic about this so it is a matter of time before one figures it out. Me too would like a single cell XHP so follow these threads like a hawk.
I'm designing a driver, should be able to do 6 amps or so to a XHP50/70, or 4 amps to a XHP35, from a single AA (NiMh only, alkaline will be limited to only 3 amps).
Right now the best way to accomplish this is with a Zener modded driver and 2- 18350’s. At least until someone can make one both small enough and robust enough. That or get someone to make you a longer battery tube for 2x 18650’s.