What you are asking for is a very specific feature. If indeed it is absolutely necessary to your site and if there is a programmer who can write the search specific script then why not bite the bullet and pay the programmer to write it? If it helps your business, then just do it.
I use Atomz
http://www.atomz.com/ search for the Xara Xone which has grown quite large and unwieldy over the 15+ years I have been running it. Atomz search is unobtruisive, does not have a big logo on it, and can be customized to your site's color scheme. Once it goes through and indexes your site it is very quick. And you can search for several words. (Thanks SS for the lead to this).
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