Since the latest release of the jQWidgets Tookit, we have a powerful jQuery ComboBox which we named jqxComboBox. In this post we will share some details about the features of this jQuery widget. A good jQuery ComboBox should be able to render more than simple strings. jqxComboBox allows you to render any kind of HTML you may want to have in the drop down list. In addition, it supports filtering which allows end users to search among the items and has full autocomplete support. While you type into the input area, the combobox will automatically select the first matching item. jqxComboBox has inbuilt keyboard navigation support and end users may use the keyboard arrows to navigate through the items and open or close the dropdown by using the Alt + Down/Up arrow key combination.
See the jqxComboBox in action in our
Online Demo. 
i could not find combo demo.
Here’s a link to jqxComboBox demos: http://www.jqwidgets.com/jquery-widgets-demo/demos/jqxcombobox/index.htm