In our website, we are using a custom implementation with an iFrame.
Specifically, the iFrame loads this page
(it's Minitek Smart Search menu item with the tmpl=component parameter that loads only the component section of the page).
But you can achieve a similar result by just using the Minitek Smart Search module. You just need to enter the module inside a modal window that is triggered with a button.
In order to do this, your template must support modal windows. Or you can use a 3rd party extension for modal windows.