Available battery voltage/voltage combinations.

[Mr.BeSoBeautiful]

I currently use a Maxi Roughstack v2.I use a 18650 3.7v battery for everyday purposes and 2 16340 3v batteries for 6v vaping occasionally. I'm looking for a battery or battery combination that would allow for 4v and 5v vaping. I've done some searching on the forum for a list of available batteries and voltages but have been unable to find them. I'm trying to achieve variable voltage through batteries vs. spending an arm and a leg on a vv mod or a cheaper vv box mod which would be more cumbersome for me to carry around for every day usage. Any help would be greatly appreciated.