We'll create fresh WordPress site with 404 Simple Redirect installed. You have 20 minutes to test the plugin after that site we'll be deleted.
This plugin hooks the normal WordPress workflow in order to determine if the request is processing will cause a 404 HTTP error. In that case it prevents WordPress to do any other processing and sends the user to the page defined in the plugin options.
A working and simple solution.
For more information about this plugin you can check the official page.