Maybe you haven't heard, but Samsung has been making folding phones that fold up to be very small. The Galazy Flip 7 is pretty much what you describe as far as easily being able to fit in a pants pocket, has plenty of battery life, high-res screen, and it even flips out to have a large screen. No, folding phones are not a gimmick, been using a fold 4 for a few years and it's been amazing.
https://www.samsung.com/us/smartphones/galaxy-z-flip7/buy/ga...