I wasn't aware of a similar command-line utility for Windows, and writing one seemed like a simple enough matter, so I decided to write one. The utility would just need to get the value of the PATH environment variable, parse the individual directories out of the path, then do a "file exists" check in each PATH folder, checking for the specified file name.
I was able to put the program together fairly quickly, and it seemed like something that people might find to be generally useful, so I spent a little bit more time to polish it, then added it to the utilities page on my homepage for download as PathFind.exe. The extra polish included automatic searching for the file with extensions from the PATHEXT environment variable (.com, .exe, .bat, and so on) for files for which no extension is specified (so the user can search for just "iisreset" instead of having to search for "iisreset.exe"), as well as things like input validation, error handling, and a help message.
As it turns out, Microsoft also has released a similar utility, where.exe, available for download with some of its resource kits and SDKs such as the Windows 2003 SP1 Platform SDK (but not apparently available as a stand-alone download). The where.exe utility supports wildcard searches and some other advanced options, but doesn't support automatic PATHEXT extension searching.