Using one of these Flashlights from MadVapes
http://madvapes.3dcartstores.com/Flashlights_c_24.html
I used this switch but there are others you may prefer
http://www.madvapes.com/Mini-Push-Button-Switch--Black_p_2149.html
Easily fits an 18500 battery but all I had was 14500 batteries and this diagram shows how to use one of them. You do not need a adapter for the 18500 battery and would be the way to go.

Hope this helps and hope it worked for you for I Love this Mod.
Picture of my Flashlight Mod I glued a cap on my button.

