I tried to find some tools, but didn't find anything.
I think gamecube ciso is removing unused data from ISO (like the WBFS format for wii games).
It was thought impossible to re-create a full ISO from a Wii wbfs file format, but someone made it years later (after the wbfs format was created).
I don't think the same thing has been done for gamecube.
The tool is called Nkit, from developer Nanook.
old thread :
https://gbatemp.net/threads/new-app...isc-images-in-playable-formerly-swiit.533402/
New thread :
https://gbatemp.net/threads/nkit-re...-and-gamecube-disc-images-as-playable.548479/
Even though it was created for Wii and WBFS, the authors added new format support and gamecube support too.
He even released his own compressed format for gamecube called nkit.iso
That tool can convert Wii games and gamecube games file format. I think you could try. Nothing to lose.
Maybe it will detect scrubbed iso (ciso for gamecube) and can regenerate missing data to make a full 1.35GB ISO.
But I didn't test, I didn't see any mention anywhere that ciso were supported.
One the wiki, there's also no mention to ciso at all.
https://wiki.gbatemp.net/wiki/NKit/UserGuide
But, maybe you can try the "recover" option ? it's converting GC iso to GC iso. (unless it's Fix94's format for compressed ISO, these are not ciso; just smaller files rebuilt to follow the iso convention format)
Fix94 format is using "Gamecube ISO compress", and was used to play gamecube game with DML (old Wii app to play gamecube from SD, before nintendont was created).
the link on first post is 0.2, but there is a v0.3 if needed (maybe even newer?).
You can drag-drop the file into the command line tools, or use the GUI app.
Note: if it tells bad CRC, it's maybe because you are using an outdated redump database.
don't worry and compare your generated iso CRC against redump yourself. (or update the database)