ThemesWP

Using Ultimate Custom ScrollBar for customize scrollbars, you get a very elegant and unique site. Consistent scroll behavior for every device. You can change scrollbar size, colors, animation, position from this settings page.
Plugin Features
<ul>
<li>Simple installation & activation</li>
<li>Supported touch devices.</li>
<li>Unlimited colors.</li>
<li>Lightweight.</li>
<li>Enable/Disable Option.</li>
<li>Easy Option Panel.</li>
<li>All browser supported</li>
</ul>
Free Options
<ul>
<li>Enable/Disable ScrollBar : You can enable or disable scrollbar using this option.</li>
<li>Cursor Width : You can increase or decrease cursor width using this option.</li>
<li>Rail Background Color : You can change rail background color from this color picker.</li>
<li>Cursor Color : You can change cursor color from this color picker.</li>
<li>Auto Hide Mode : You can select scrollbar auto hide mode from this selectbox.</li>
<li>Included all free options.</li>
<li>Cursor Border : You can control cursor border using this option.</li>
<li>Cursor Border Radius : You can control cursor border radius using this option.</li>
<li>Scroll Speed : You can control scroll speed using this option.</li>
<li>Mouse Scroll Step : You can control mouse scroll step using this option.</li>
<li>Emulate Touch : Enable cursor-drag scrolling like touch devices in desktop computer.</li>
<li>Minimum Cursor Height : You can set the minimum cursor height.</li>
<li>Bounce Scroll : Enable scroll bouncing at the end of content as mobile-like.</li>
<li>Horizrail Enabled : You can control horizontal scroll.</li>
<li>Rail Align : You can control alignment of vertical rail.</li>
<li>Rail Valign : You can control alignment of horizontal rail.</li>
<li>Enable Mousewheel : You can control Mousewheel using this option.</li>
<li>Enable Keyboard : You can enable or disable keyboard events using this option.</li>
<li>Hide Cursor Delay : You can set the delay in microseconds to fading out scrollbars.</li>
<li>Enable Scroll On Selection : You can enable auto-scrolling of content when selection text.</li>
<li>Cursor Drag Speed : You can set speed of selection when dragged with cursor.</li>
</ul>

Ultimate Custom ScrollBar

Using Ultimate Custom ScrollBar for customize scrollbars, you get a very elegant and unique site. Consistent scroll behavior for every device.

WebXApp

<h4>WordPress custom scrollbar</h4>
WordPress custom scrollbar is highly customizable WordPress plugin. Features include vertical and/or horizontal scrollbar(s), adjustable scrolling momentum, mouse-wheel, keyboard and touch support, ready-to-use themes and customization via CSS.
<h4>Features</h4>
Custom Selector Scrollbar 
Full page Scrollbar 
Single Content Scrollbar 
Vertical and horizontal scrollbar support 
Highly Customizable 
ScrollBar scroll speed control 
Responsive for all devices 
Easy to handle

Scrollbar by webxapp – Best vertical/horizontal scrollbars plugin

Customizable WordPress scrollbar plugin. Vertical/horizontal, momentum scrolling, mouse-wheel, keyboard, touch support, themes, CSS customization.

Ultimate Custom ScrollBar vs Scrollbar by webxapp – Best vertical/horizontal scrollbars plugin