Please add pi.search_assistance.php to /deploy/system/expressionengine/third_party/search_assistance/pi.search_assistance.php

404.html

{layout="_layouts/_main"}

{layout:set name="extra_metas"}
	<meta name="robots" value="noindex,nofollow,noarchve">
{/layout:set}
<div class="wrapper">
		<div class="page__main">
			<nav class="nav nav--breadcrumbs">
				<ul>
					<li><a href="/">Home</a></li>
					<li>Page not found</li>
				</ul>
			</nav>
			<div class="page__body page__body--listing">
				<h1>Page not found</h1>
					<p>Sorry, the page you are looking for could not be found.</p>
				{exp:search_assistance segment="{last_segment}" parse="inward"}
					{exp:low_search:results keywords="{segment}" limit="10"}
						{if count == 1}
						<p>Here are some suggested pages:</p>						
						<ul>{/if}
						{exp:switchee variable="{channel_short_name}" parse="inward"}
							{case value="new_equipment"}
							<li>
								<a href="/used-equipment/product/{url_title}">{title}</a>
								{channel_title}								
							</li>
							{/case}
							{case value="sundries"}
							<li>
								<a href="/sundries-tools/product/{url_title}">{title}</a>
								{channel_title}
							</li>
							{/case}
							{case value="used_equipment"}
							<li>
								<a href="/used-equipment/product/{url_title}">{title}</a>
								{channel_title}								
							</li>
							{/case}
							{case default="yes"}
							<li>
								<a href="{auto_path}">{title}</a>
								{channel_title}
							</li>
							{/case}							
						{/exp:switchee}
						{if count == total_results}</ul>{/if}
					{/exp:low_search:results}
					<p>For more results please check out <a href="{path='search?keywords='}{segment}">search results for '{segment}'</a></p>
					<p>&nbsp;</p>
				{/exp:search_assistance}
			</div>
		</div>
	</div>

pi.search_assistance.php

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

/**
 * Search assistance Plugin
 *
 * @category    Plugin
 * @author      
 * @link        
 */

$plugin_info = array(
    'pi_name'       => 'Search assistance',
    'pi_version'    => '0.1',
    'pi_author'     => '',
    'pi_author_url' => '',
    'pi_description'=> '',
    'pi_usage'      => Search_assistance::usage()
);


class Search_assistance {

    public $return_data;

    /**
     * Constructor
     */
    public function __construct()
    {
        $this->EE =& get_instance();
        $data = ee()->TMPL->tagdata;
        $segment = ee()->TMPL->fetch_param('segment');
        $segment = str_replace('bakery','',$segment);
        $segment = str_replace('-','+',$segment);
        $this->return_data = str_replace('{segment}',$segment,$data);
    }

    /**
     * Plugin Usage
     */
    public static function usage()
    {
        ob_start();
?>
<h3>Search assistance</h3>
<p></p>
<hr/>
Include your documentation here...
<?php
        $buffer = ob_get_contents();
        ob_end_clean();
        return $buffer;
    }
}


/* End of file pi.search_assistance.php */
/* Location: /system/expressionengine/third_party/search_assistance/pi.search_assistance.php */