wooassist

This plugin adds a custom field in the checkout page to ask your customers where they heard about your store.
This plugin also offers an “Other” field where your customer can provide a specific answer in a separate textbox.
Features:
<ul>
<li>Easily change the labels and choices for the custom field in the checkout page.</li>
<li>View reports on the “Reports” section in WooCommerce.</li>
<li>Enable/disable the custom field to be required on checkout.</li>
<li>Enable/disable the “Other” field.</li>
<li>Modify order statuses you want to include in the reports.</li>
<li>Export Orders with Customer Source field</li>
</ul>

Where Did You Hear About Us Checkout Field for WooCommerce

Adds a custom field in the checkout page to ask your customers where they've heard about your store.

Wombat Plugins

studiowombat

This lightweight plugin adds a bottom bar on mobile devices, like on the StoreFront theme.
FEATURES 
 * The bar links to your cart page. 
 * Allow searching products from the bar. 
 * Link to you account page. 
 * Change the design’s colors. 
 * The cart icon updates when a product is added to cart.
REQUIREMENTS 
* PHP 5.4 or higher 
* WordPress 3.7 or higher 
* WooCommerce 3+

WooCommerce Bottom Bar for Mobile

This lightweight plugin adds a bottom bar on mobile devices, like on the StoreFront theme.

Where Did You Hear About Us Checkout Field for WooCommerce vs WooCommerce Bottom Bar for Mobile