So after a whole lot of searching in the game, through the game files, and online, I've finally managed to find all the Olaf Eye Orbs!

There are at least 135 of them (!), possibly more, though I really doubt it. After the 130th, you get the final Olaf poster, so the last five seem to just be extra. Nothing else seems to unlock from getting them, so I assume they just put extras in to make it a bit easier to get all the posters.

Having said that, I'm not actually sure where the 135th is exactly, just that I always end up with it at some point in the course of picking up all the others. Also, there are 5 in Josephine's house that are pretty ridiculous in terms of how they're hidden.

Here's a google spreadsheet that lists all the orbs and letters, their locations, and the maps they're in. Apologies for the short form notes about where they are - I'm planning on making a video showing all their locations in better detail, I'll post that when it's done.

https://docs.google.com/spreadsheets/d/1AaiuSUn4pTmkjuhvTRSgKNbTIMYkNvFZiXzKAjr4ZMA/edit?usp=sharing