The mon pendant is likely the best idea.
You could also 100% hp scroll your hat. I did that with my hermit's zhelm until I later relooted. I didn't want to blow it up anyways with 30%s and 70%s.
Any equips slots you don't really fully untilize, like if you don't have a real good cape you could go for an hp cape, or maybe earrings.
There is also just putting ap points into hp, or blooding your character, but thats only sometimes advised for particular bosses. You can possibly later take it out of mp if you where int gear while leveling but that gets expensive and confusing to do all that. But just so you know those options too.
The mon does seem to be your best choice tho :)