Nimesh Gorfad

Inquiry Button for WooCommerce allows you to add a customizable WhatsApp inquiry button to your WooCommerce product pages. This makes it easier for customers to contact you directly for more information about your products.
Key Features:
<ul>
<li>Enable or disable the inquiry button.</li>
<li>Customize the WhatsApp number, inquiry message, and button text.</li>
<li>Seamless integration with WooCommerce product pages.</li>
</ul>

Inquiry Button for WooCommerce

Adds a customizable WhatsApp inquiry button to WooCommerce product pages.

tathemes

Inquiry Form for Woocommerce just replace your add-to-cart button by a custom button which will bring a popup with a form. The data of the form will go to the admin email. 
If you need to put a quotation or inquiry form instead of add-to-cart in Woocommerce single product page then this plugin is fantastic.
Demo:
<a href="http://akramul.com/plug-dev/shop/" rel="nofollow ugc">LIVE DEMO</a>
<h4>Features</h4>
<ul>
<li>Simple & Intuitive</li>
<li>Option for using built-in form or custom form</li>
<li>Bootstarap switcher</li>
<li>Very easy to use</li>
</ul>

WDU Inquiry Form

WDU Inquiry Form will replce default Add to cart button

Inquiry Button for WooCommerce vs WDU Inquiry Form