Where to find the file to edit the Waiting List pop-up?

[Danab]

I think I am blind and lacking caffeine LOL. I cannot seem to figure out how to edit the pop up window for the customer waiting list? I have suddenly started getting spam on the popup and I realized the re-Captcha is gone on it. I searched and I cannot figure out where the file is so I can see about reverting/editing it so the re-captcha comes back.

Thank you!
Dana