Go to Welcome to MadVapes LLC and check out the piece parts they sell for mod building. You can buy a variable voltage mod already assembled for $35. You'll need 2 14500 IMR batteries and a charger. That will add about $20-$30 to the total cost. They also sell regulator chips, miniature digital voltmeter modules, and atty connectors, as well as all the other parts you will need to assemble a good mod that looks store bought.
Variable Voltage Box Mod
Variable Voltage Box Mod

led are fun, and can let you know when the batteries need recharging......kinda the same as, hmmm no more vapor coming out, guess the batteries are dead...