[cctalk] Searching for Cisco Catalyst 3920 Token Ring switch firmware

Hello all, As the subject implies, I'm on a search for Cisco Catalyst 3920 Token Ring switch firmware. AFAIK, these units are actually from a company Cisco acquired. They definitely don't run IOS or CatOS, and have an odd full-screen interactive menu interface. It worked when I received it, but after a power outage, the firmware got corrupted, leaving all interfaces effectively dead. It seems that there is no official way to get a copy of the image from a working unit, either, as I've had people attempt it. The general naming pattern is supposedly cat3900-main-gz.x-y-z.bin, where [I believe] x, y, and z would represent some sort of version information. If anyone has this file, or any leads as to where I might find it, I'd be forever grateful. Apparently, even Cisco employees cannot find it nowadays. Thanks much, jpw