I fetched all Sansa c200 and e200 firmwares I could find and wrote a script that scanned all of them for new mi4 keys, and it only lead me to a single new key (for the Sansa C200 A1.00.03 firmware version).

Another key added, and mi4code 1.0.2 is up on the mi4code page.

This was easily done thanks to Zefies’s firmware collection!