I highly recommend using a standard DC-DC converter to bring down the voltage from a standard AC-DC power supply (sized for whatever wattage you'll be using). The OKR-T10 is a very popular converter being used for DIY projects and, IIRC, can get you up to 50W. You can use a 12V power supply, easily available everywhere, and adjust the voltage via a potentiometer (basically, a resistor with a knob to adjust its value) to create a VV
mod. There are even box mod kits using the OKR-T10. You can go a lot higher than 10A though, easily to 30A, and a lot higher for a lot more money.
You could bring the voltage down via a voltage divider but the voltage you drop gets wasted as heat...a lot of heat.

Better to use a converter to adjust the voltage. Makes it easier to change voltages too as a VV mod might need tweaking for each coil you build unless they're very close in resistance.
You could also just use a DNA40 board with a 5V AC-DC power with its "trim" voltage adjust set to 4.2V or lower. Or, for those who need more power, a DNA200 board and a 12V power supply. You only need three tiny resistors to fool the board into thinking it's connected to three
batteries. This way you get VV and VW control.