I admit to my shame I've never read The Moon is a Harsh Mistress (I know, I know) but I have read Door into Summer and I think it could be easily adapted. I mean, they adapted All You Zombies and that was truly a challenge visually (for reasons I won't spoil here). In comparison, Door is a more straightforward time-loop + betrayal story of the kind that can be adapted to the big screen...
Edit: unless you're referring to an icky age-related situation, but that could be fixed in the movie adaptation to make it less icky.
Edit: unless you're referring to an icky age-related situation, but that could be fixed in the movie adaptation to make it less icky.
Edit 2: wow, and it was made into a movie... by the Japanese: https://en.wikipedia.org/wiki/The_Door_into_Summer_(film)