how to get librarian

[Aponez]

Is there another way to get a librarian? I chose a paladin on my first offer. And the rest of the missions i have only ever seen chaplain and purifiers offered. Or is my luck just bad.

 

[HRDiagram]

I think I had one show up once in the requistion options at the end of a mission. (Or was it a Chaplain? )
I missed him because I did not have enough requsition points and at the time I didn't think I would not come across another one.
I am well beyond day 700, and it's only happened once (when I was given the choice, I picked a Purifier, while I got two Paladins through other events).

edit:

confirmed, I just got a Librarian from the requisition at the end of a mission (and got a Chaplain earlier)