The Plugin Forge

Quick Checkout adds a “Buy Now” button to your WooCommerce product pages. Customers skip the cart entirely and land straight on checkout.
<h4>Features</h4>
<ul>
<li>Buy Now Button — Adds product to cart and redirects to checkout via AJAX. No page flicker.</li>
<li>Quantity Selector — Optional +/− input inline with the button so customers can adjust quantity before buying.</li>
<li>Sticky Buy Now Bar — Fixed bar at the bottom of the screen that appears when the main button scrolls out of view.</li>
<li>Per-Product Overrides — Override button text, color, and redirect per product. Disable the button on specific products.</li>
<li>Variable Product Support — Button stays disabled until a variation is selected, then activates automatically.</li>
<li>Stock Urgency Message — Shows a customisable low-stock message above the button. Custom text, background, and text color.</li>
<li>Advanced Styling — Solid, Outline, Gradient, or 3D style. Custom colors, size, border radius, and width.</li>
<li>Category Targeting — Limit the button to specific product categories via AJAX-powered search.</li>
<li>Shop Page Support — Show the button on archive/shop pages with configurable hook position.</li>
<li>Analytics — Track button views, clicks, and conversion rates per product. Filter by Today, 7 Days, 30 Days, or All Time.</li>
<li>Shortcode — <code>[spcb_buy_now product_id="123"]</code> — place a Buy Now button anywhere.</li>
</ul>
<h4>Redirect Options</h4>
<ul>
<li>Checkout page (default)</li>
<li>Cart page</li>
<li>Custom URL</li>
</ul>
Per-product redirect overrides work independently of the global setting.
Built by <a href="https://thepluginforge.com" rel="nofollow ugc">The Plugin Forge</a>.
<h3>Privacy</h3>
This plugin does not collect, store, or transmit any data externally. Analytics data is stored only in your WordPress database and deleted on uninstall.

Buy Now for WooCommerce – Quick Checkout by TheForge

Add a Buy Now button to WooCommerce products. One click — skip the cart, go straight to checkout.

kraftpixel

Here is a plugin that allows your e-commerce site to float a customizable buy button at the bottom of your mobile screen after a certain scroll-depth that you enter (the default is 200). This should help you in your e-commerce conversions. The goal of the plugin is to help you improve e-commerce conversions on your mobile devices.
You can tweak the color, the button action — add to cart or buy now and more.
Please note: 
1. The buy button will only be visible on mobile devices. 
2. This is a plugin in beta phase; please give your feedback on the plugin forum on WordPress.org

Floating Quick Buy Button for WooCommerce

The floating buy button plugin for WooCommerce to help improve e-commerce conversions on mobile. Plugin developed with love at KraftPixel.

Buy Now for WooCommerce – Quick Checkout by TheForge vs Floating Quick Buy Button for WooCommerce