SonicFileFinder is a free add-in for Visual Studio that allows a fast and convenient search for any file within every Project of the loaded Solution by entering the complete filename or just a part of it. The found file(s) can either be edited with a single keystroke or a Windows Explorer / CommandLine prompt can be opened at the file's location.

You can get it here:

jens-schaller.de/sonictools/sonicfilefinder/index.htm