Louis

This WordPress Plugin makes the default search also search based on meta data.
<ul>
<li>No setup required!</li>
</ul>

WP Search Include Meta Data

License: GPLv2 or later WordPress plugin to include post meta data when using the default search

boostetonwp

Stéphane Lion

Boost the custom fields of WordPress with this plugin: 
– Simplified creation of fields when writing your posts and pages. 
– Activate the widget to propose to your visitors the search on your fields. 
– Customize the result of the search results in the options of the plugin. 
– Insert the shortcode in your content to display the fields. 
– Insert a search form in your pages or articles.

Search For Custom Fields

Create your own fields for your posts / pages and propose a search based on these fields to your visitors.

WP Search Include Meta Data vs Search For Custom Fields