Flickr user jeffs46h3 has shared a batch of found photos from the sixties depicting the Sinclair "Dinogirls." After the 1964 World's Fair, Sinclair took the dinosaur models on a promotional tour. At some point in 1967, they stopped in Paramus, NJ, and locals had the chance to see them on flatbed trucks in the Garden State Plaza shopping mall parking lot. Someone with shaky photographic skills was on hand to document the raging fun that was had, and we're the beneficiaries!
I'd imagine that the models were hired locally, as I haven't found any mention of them elsewhere, and Jeff is the only one to use the term "dinogirl" to describe them. If you have any more details (or were a "dinogirl" yourself), feel free to let me know!