Configure nginx to display another html file when a file is present

Hello

I'm new to nginx

I'm attempting to have nginx redirect a request from a URL to another page that display something like "Deploy is in progress" so that the main URL is not available. I need to do this through a file, have nginx check if the file is present and then show the alternative html file.

I've checked the try_files directive but I don't think that's the route to go, could someone please help?