The Hogle Zoo website says "We have 2 out of the 4 remaining Hanuman Langurs in the US AZA zoos" so it sounds like they are basically gone from North America now. From some googling I get the impression that zoos which had them mostly obtained them from the breeding group which was at San Diego. If someone knew the origin of San Diego's initial imported animals they might turn out to be pure, but it is just as likely they are hybrids as the various species were formerly all lumped as one so there would have been no reason to keep individuals from different places separated.
Some googling shows that the San Diego animals were originally imported direct from India (perhaps in 1972 - mostly research papers on study groups only show the abstracts which makes it difficult). There were also groups at some of the universities, notably at Berkeley, which were also originally imported from India.
Obviously being imported from India doesn't really help with any specific IDs because all the species come from India. Most animal exports would have been from Delhi and Calcutta, but even knowing that wouldn't be a conclusive answer because animals could have been sourced from anywhere in the country - although (unlike Rhesus Macaques for which massive numbers were needed) any exported Hanumans would probably have just been caught locally to the export city.
However I spent a little bit of time looking through the Zoochat galleries and Google Images for animals in American zoos, and I'd say they are just a hybrid mix. The species can be told apart (generally speaking) in such ways as tail carriage, colouration of the body, limbs and paws, the shape of the head crest, etc - and most photos just show messy-looking beasts.
