I've coded up an external that is similar to the now-disappeared (and always unsupported) findfolder object. I'm calling it "folderman", as it uses Apple's Folder Manager functions, and of course "folderman" sounds like some geeky superhero...
I'm attaching the first draft, a UB version. It only takes a bang message, and in response outputs the path to the user's preferences folder. It works here in Max 4.6.2.
In addition to the UB build, I'm attaching the source code, Xcode project file, and an example Max patch. Please note that, in order to build folderman, "Folders.h" (from the standard Apple-distributed OS X SDK) must be in the Header Search Path of the Xcode project settings.
Although this build works, I could still use some feedback on the source code. I'm not sure it's the most solid piece of work... it's short, and well-commented, so should be easy enough to read along.