Actually, I was just searching for the same thing. You've actually found more info than I have, I didn't even know that SanDisk made those "Mp3 Companions". I'm interested as well if there's any universal-brand players.
I've been looking at MP3 players until my head hurts. Are there any out there that will play from ANY manufacturer's flash drive? I bought a cheap 128mb Lexar Jumpdrive player awhile back for my wife and like it well enough, but it won't accept another manufacturer's flash drive. I have a 1GB Sandisk Cruzer drive I use to bring work home - it would be great if Sandisk's Cruzer Micro MP3 Companion would take a regular Cruzer drive, but nooooo....only Cruzer MICRO drives.
Kind of sucks, the manufacturers crippling their players so they only work with their own particular series of flash drives. Even the slightly cheesy "VR3 Virtual Reality Sound Labs MP3 Modulator" at Walmart will take any manufacturer's flash drive. Wish they made a standalone player.