Here is a nice simple box mod that's easy to hold and has lots of room for fuses. A real snap to build, nothing complicated here. Added BOM.

here is the BOM
1 18650 protected lithium battery
1 Ecig connector, I used a 510 to 510 connector but you could use a 510 to EGO adapter if you want to have the EOG threads.
2 1" X 1/2" brass shims I used 0.018" thick or .5mm. I had on hand
1 momentary push button .. 7/16" diameter hole 3 amp minimum.
6: of 22 ga. wire.
10 3mm X 1.5mm magnets. I didn't need them mine snapped together. But maybe after use I will add 2 or 4 as needed.