Hi. I'm not sure of any good scripts. Seems to me you should be able to throw something "clever" together pretty easy.
If i searched 'designer glasses' i want to see results with designer brand sunglasses not just items with the word designer in the title
I would have a drop down/list that could be selected with pre-poulated search values. Such as 'Designer Sunglasses', 'Cheaper Sunglasses', etc... Or have more than one. One that's like that and then another that searches say, manufacturers. Depending on the set search, run the appropriate queries. But still have a search field that can be typed in allowing the users to really drill down a specific search.
As far a pagination. There are lot's of good tut's out there and I'm sure you could find a nice, useful script to use for your needs.
Here is a good one I've used a few times. [phpfreaks.com ]. The script may have to be tweaked in certain ways for your needs which is normally the case with any script.
Just figured I'd toss you a few ideas. Searched are aimed at returning results you will most likely need and want. Give the user the option to choose the type of search they want to do. Search by category. Search by manufacturer. Search by Color. Or type a search for a broader range of results. Just my $0.02