Website directory search... multisite,buddypress

Hello to the worlds most awesome wordpress Community,

I`m sorry for my bad English... But I´m trying to describe my problems and questions as well as possible...

I want to categorize my multisite Buddypress installation.

Please have a look at meinestadt...

There is a searchbox where you can select from which town you come from.

Then you get informations about your hometown after selecting your town.

I think that each town is a multisite subdirectory or subdomain in

Do you know a searchbox plugin or widget which does the same like on

Hope that somebody can help me...