Toothed, I only collect old pocket knives so I'm not familar with the current waterfall offered by Bulldog, Case, Remington, Winchester, and any others being made today. I do know they are probably not celluloid but a modern material such as acrylic.
As for older knives (pre 1940's), all the good American brands offered waterfall that was active. I have some New York Knife, E.C. Simmons, Robeson, and Remington examples that are all very nice.
I'd suggest doing a search on eBay if you don't have access to a knife show or club. Be sure to check the "titles and descriptions" box on your search. You might also want to email the seller and ask about the action of the waterfall.
A waterfall theme would make a nice collection in itself.
Good luck.