MMC Replay – MMC64 and Retro Replay combined in one cartridge, with some improvements
Micromys – An adapter that allows connecting PS/2 compatible mice (including wheel-support) to C64 and Amiga joystick-ports (and all other computers that share the same pin-configuration).
Amiga clock port compatible addons for MMC64, Retro Replay and MMC Replay:
RR-Net: A C64-compatible Network-Interface. Comes in 2 shapes, the old long RR-Net fits Retro Replay and MMC64 (though partly blocking the latter's passthrough expansionport), the new L-shaped RR-Net2 fits MMC64 and MMC Replay and was built with MMC Replay in mind.
Silver Surfer: Highspeed RS232 Interface for the C64. Fits onto Retro Replay, MMC64/Replay compatibility unknown.
mp3@c64: hardware mp3 decoding from SD card. Made for MMC64, Retro Replay and MMC Replay compatibility unknown.
Keyrah – An interface that allows the connection of Commodore keyboards to USB-capable computers