Password protect certain portfolio projects

Hi,
This is my site https://www.zteff.com

I’m looking to password protect only certain portfolio projects so that you can still view the thumbnail but upon clicking on it, you get prompted for a password. Whether it be a popup, or you are navigated to a page that prompts you for a password, I don’t mind.

I’m aware wordpress kind of offers this but the password protect feature for portfolio only hides some text.. not the entire project which isn’t what I’m after. I want all the information including images to be hidden until you enter the password. Also not wanting it to display “protected” in the title.

See this here

The theme I’m using is Willow by Solopine. I did raise this with them but they’ve said that WordPress has a plugin for this but I’ve yet to find one.

Is there a way of doing this?

I need this option as it’s good for prospective clients to be able to see all of my work.. but as some work hasn’t yet gone to print etc, I legally cannot have it live on my site.

Thanks