Aaron Axelsen

The Advanced Search Widget is designed to be a replacement to the defaut search widget. The Advanced Search Widget allows you to search for only a 
specific post type and also select which fields to query (title, content, tags).
In addition, it is also possible to place multiple widgets onto the sidebar to search through different custom post types.

Advanced Search Widget

Allows you to add a widget to search custom post types along with other options

ajberasategui

This plugin provides a Search Widget similar to the default WordPress one but with the abilty of adding category select 
lists to restrict the search query to only those categories.
Any comments, reviews, support questions are very much welcome!!!

AB Categories Search Widget

Insert a search form widget that allows visitors to add category filters to the search query.

Advanced Search Widget vs AB Categories Search Widget