I just picked Adam Pollack's book on Fitzsimmons a couple weeks ago, so I've been on a Fitzsimmons kick. Perfect timing.
Here's the highlight reel of Fitzsimmons fighting Bill Lang, when he was well past his prime, but I believe it's the 'best' quality footage of Fitzsimmons in the ring.
https://www.youtube.com/watch?v=DcsJJqBi67k