Easiest way to get MMBs?

I'm thinking about getting MMBs so I can get some WH Books, but not sure how to farm for them. Is there an easy way to get them, apart from bossing major monsters (Zakum and things like that)?

The boxes you get from the mesoranger exam can give MMBs, so you could farm those.

The boxes you get from the mesoranger exam can give MMBs, so you could farm those.

Really? I never came by those. I've found Scrolls, Chairs, Trait items, Ore pouches, Mounts, but never MMBs. ._.

They're one of the rarer items to get from Mesoranger boxes, I would assume. I can personally confirm I've gotten at least 2. Another way to get MMBs is from Rare Monsters, that are at least level 120+? I'm not too sure if they changed it to level 100+ monsters as of the Tempest patch. There's also event MMBs, from coin shops. We'll be getting the tempest coin shop on the same day of Luminous's release, I think. Which is December 5th?[

Edit: Another method to get MMBs is from Monster Park bonus boxes. Unfortunately, getting a bonus stage is quite uncommon, and even getting a goodie out of the boxes is unlikely.