We do have a search plugin you can used for this. Visit Tools >> Edit >> Plugins >> Utilities (section) >> Search plugin.
The open search function of your site can work with our "Search Plugin". To integrate this feature. In the tools click on the 'Plugins' tab. Then locate and click on the 'Search' plugin. Here you will be prompted to include a search query string "OpenSearch URL Template *". In this field enter: http://www.website.com/?q={searchTerms}. Save.
This will allow your visitors to search your sites listings.
Kind regards,