Florian Egermann

Unlike other “maintenance mode” plugins, this plugin lets you redirect visitors to one of your existing pages (no need to edit a maintenance template to make it look like your website).

MM Maintenance redirect to page

Simple maintenance mode  – redirect all visitors (except admins) to a page of your choosing.

Sirius Pro

Simply enable maintenance mode and redirect users to custom message. This plugin allows you to enable maintenance mode for a specific date range without modifying the code and it works with most of the available themes. Just install and activate this plugin to enable maintenance mode and redirect all users.
Read more about this plugin on <a href="https://siriuspro.pl" rel="nofollow ugc">WordPress</a> blog.

Maintenance Mode Redirect

Simply enable maintenance mode, redirect logged in user and show custom message instead of WordPress homepage.

MM Maintenance redirect to page vs Maintenance Mode Redirect