Smallest 18650 flashlight
Cree XPG2 or better
Where to purchase?
For the money, you’ll have a hard time beating the UF2100 or one of the variations. I don’t think there’s much out there smaller than this one and for around $15.
I like that Palight V60 but nobody really has one yet.
UF 2100 is a good option, but if you're going to use an xp-g2 might as well use a 2.2a 6x7135 V2 driver. Then at that point might as well start off with a bare host.
This one, along with this reflector would be a good combo. $11.50 for the host and $2.90 for the reflector (host is really a high quality piece... just reviewed one here somewhere)