The current Comet Firmware level is 2.25.
The current Ion Firmware level is 1.83.
If your EXOGAL Product is already at this level, please do not perform an upgrade to it! It's likely to work fine but don't risk "bricking" it for no reason!
The Upgrade package for the Comet can be found here. The upgrade cables come packed with the Ion. The Ion has not received an update since its release.
If you want to update the Comet without an Ion, you will need to purchase an FTDI cable. Search Google for "FTDI TTL-232R-5V-AJ cable". A good global source is Mouser Electronics.
Update the Comet by following these instructions.