How can I increase my chances of finding the Missing Poster?

With the Afterbirth expansion, there a new way to get to The Lost, by sacrificing Isaac in the Sacrifice Room while holding the Missing Poster. The bad news is, I don't know where to get the Missing Poster. I have already unlocked it, but I can't find it.

So my question is: what is the best way to unlock The Lost in Afterbirth?

Solution 1:

As pinckerman mentions, the Fortune Teller is a good way to spawn a large number of trinkets quickly, particularly if your luck stat is high.

Another great way is by using Mom's Box, an active item with a 4-room recharge that spawns a random trinket. This is nice because it's actually a pretty good active item, so you don't have to sacrifice your progression to try and farm trinkets, and because you can use it many times during a run, especially with how often batteries drop in Afterbirth. This works especially well if you're able to break the game, giving you unlimited batteries; you're pretty much guaranteed to generate Missing Poster at some point.