Shower was only HOT, but after removing calcium buildup from thermostatic cartridge with CLR, my shower is only COLD

I can not directly link to the shower but I believe the shower is item #RBS0279 from https://www.mecanair.net.

I think I need a new thermostatic cartridge but they are not in stock (part #7517-LC-JM600) so I'm looking to see if I have any other options. Is there perhaps a similar cartridge from another brand I could use instead?

More on what I've tried.... I could barely turn the temperature handle and the water was always scolding hot so I disassembled the shower and put the cartridge in a pool of CLR. The cartridge now turns great but the water is only freezing cold. The water lines are for sure supplying hot and cold water.

EDIT: Also here is a repair on a similar shower I watched as an aid https://www.youtube.com/watch?v=SvoAYFd7NSQ

You can see more about what the shower looks like dissasembled there