Sort of like the common jelly bean MC34063 switcher, but capable of fully 100% duty cycle, does it exist ?
I'm aware there are many choices from different IC makers like Linear, TI and etc, its just most of them are exotic and not that easy to source like the MC34063 or those common National Simple Switcher family ics.
It doesn't need to be highly efficient, heck, even 70% is more than enough and switching freq at < 500Khz is fine too, and if it has thru hole version, that is even better.
Targeted circuit is just a simple adjustable step down from 12 volt source to drive a DC motor (a drill) ranging from 5 volt up to full 12 volt as the source, with 2 or 3 Amp max.
Since its driving a motor, output voltage ripple and the regulation performance like transient response are not that critical.