I want to build a screwdriver or tube style mod - need help with batteries

[Godzilla]

I would like to acheive 5 volts, without having to stack more than 1 battery. Is there a battery with somewhere around 1500 mah that will fit inside a screwdriver handle, or tube?

Also, would a voltage regulator be necessary?

Thanks

 

[Para]

If you want to use ONE battery you have to boost it up. Check out Breaktru's latest. Awesome mod he made