Search plugin for webpage for users to search the site

I need a search plugin that I can place on a webpage for users to use. I’ve found a couple of plugins, but those are for the admin area. Also, I want to integrate it’s functionality into an input text-box I already have, so I keep the same design.

Do we have something where we add a tag (eg. rel=”lightbox”) that activates an input text-box for search function?