It’s not an aftermarket replacement.
It’s a repair. They remove the damaged cells and replace them. That company is in the US (the owner is somewhere in scandinavia) – and it might simply not be feasible in the first place.
Tesla tried to charge $22,500 for new battery pack when a $5,000 repair did the trick
Not to mention that, by the looks, many of the faults can’t even be diagnosed by non-tesla certified technicians (although that’s not unique to tesla).
More importantly: the garage who repaired the pack says that this “repair” won’t last a year due to the now inherent pack imbalance. I’m not sure i agree with that, but i will say that the “repaired” battery has a considerably reduced lifespan, so at best this is a band aid.