How to restore hit point maximum?

As a DM, I’ve been using a Mummy and one of my players really lost a lot of hit point maximum. In my head, it was clear they’d go to the nearest town and ask for heal to the priest who can cast remove curse to halt the bleeding and greater restoration to get back their hit point maximum, but they only removed the curse (by spell swapping at a level up) and went on.

So I might throw another way to get their hit point maximum on the road, but what? Besides greater restoration (and wish), what are the other ways of getting back all of part of someone’s hit point maximum, especially at level 4-5?