There's another photo of Rome's Assam macaque here
Also, when I visited in 2010 Palmitos Park (Gran Canaria) had a group of around 5 talapoins on exhibit, with both species displayed together. Unfortunately they were mostly curled up balls of fur, I can't remember how many were Southern, but I remember struggling to see a definite Northern talapoin. If it was a family group, I imagine that there may be at least one survivor. I've had to repeatedly post this listing to zootierliste as it's regularly completely deleted.