How to add new search engine options in Safari for Windows?
There are a few Safari Extensions that will enable this:

http://www.macupdate.com/app/mac/35036/popsearch-safari-extension

http://safariextensions.org/detail/Search_All/

http://safariextensions.org/detail/CustomSearch/

http://safariextensions.org/detail/OpenSearch_for_Safari/