eSim guaranteed to be on either AT&T or Verizon

I never considered that I might need an alternate in the US but we’re traveling around Sequoia and Kings Canyon where our T-Mobile phones don’t work. They’re unlocked iPhones so we’re not worried about that.

Are there any high quality esims with about a weeks worth of data that we can be sure will use either Verizon or AT&T? Mostly for just maps and messaging each other.