I found the faraday isolator that was hidden in the bubble wrap with the 50:50 fiber beam splitter. The faraday isolator has 1 m long fibers on either end of a 2" cylinder, so it can't be held by any existing fiber holders. For space purposes, I am also 3D printing a fiber holder for the 50:50 beam splitter so they can be stacked on top of each other, but a Thorlabs fiber holder could also work. See attached part files.

I am currently 3D printing the bottoms. I will 3D print the tops next.