Any plugin to search posts by category?

I am developing a website for an auto dealer. On the homepage and maybe even in the sidebar I would like to place a search function which will allow the user to search for cars according to Make (e.g. BMW) and Model (e.g. 1 series). Then a page with results will show up. Users can either search by make only or both.

Is there a plugin or code that can do this?

Each Make will be a POST category and model either under parent category (daughter) or as a tag?