wpsimpletools

Puts the site in maintenance mode, redirects all non-authenticated requests to a basic responsive page (included in the plugin) or custom URL. 
Maintenance mode setting page is accessible from WP ‘Settings’ menu.

Maintenance Mode with 'coming soon' page or redirect

Simple yet complete maintenance mode plugin.

netfett

The maintenance mode only puts the WooCommerce Shop into maintenance mode, but not your entire website. Decide for yourself which text or content should be displayed.
Possible reason for the “Coming soon” mode: 
Your shop is not quite finished yet, but you want to show your visitors that a shop is about to open on your website.
Possible reason for the “maintenance mode”: 
You made an error while configuring or maintaining your products, and you can’t find the error right away. Then switch your shop to “maintenance mode” and take your time to correct the error.
And the best thing is: it’s free! 
Yes, it’s absolutely free. There is no premium version.

Maintenance mode for WooCommerce

Does what it says and is easy

Maintenance mode for the Woocommerce Shop

Maintenance Mode with 'coming soon' page or redirect vs Maintenance mode for WooCommerce