I used to get 2xAA and 3xAA boxes at R.S. It's not a project box, it's a battery box.
The 2x is for a single-battery 3.7
mod. 3x is for a regulated mod. Get the larger 3 amp button for the 3.7 2x box......
You'll need to scrounge a connector off an old battery. And of course, wire, solder, iron, and epoxy. LED and resistor optional. See modder's section.