Have you tried cutting out one of the characters , saving that and then using Google Image search (where you drop the image into the search box?
Failing that, to get more diverse characters, have you consider tracking the characters in the footage and replacing their heads? Might be more work, but if you can’t find the originals. They have a look of being created in an animation tool – preset actions – it might be that there aren’t more diverse characters in the collection.
Searching for “Adobe Character Animator” shows there is an increasing number of characters available for that software. Might bail you out.
http://www.YouTube.com/ShiveringCactus – Free FX for amateur films
https://shiveringcactus.wordpress.com/ – FX blog