Not possible anyway if Bosch won't sell spares.
In the video I linked to, the start of the chain of events that led up to the death of the motor, was caused by the owner failing to replace a bearing that the axle ran through. This bearing started to disintegrate and then the seals failed and started to let water in. The water then corroded the PCB to the point where it failed.
The bearings are a serviceable item which a competent bike shop or Bosch service centre can do. It's an interesting video that explains the problems and what led up to it and how it was an avoidable situation if the owner had replaced the bearing early enough.
The whole issue of lack of water proofness is an interesting one, looking at the ebike motor centre's website they have this to say about waterproofness of the motors:
"Is my motor waterproof?
The answer is, probably not. Currently, it would be commercial suicide for ebike motor manufacturers to properly seal a motor because this would lead to added friction and lower battery range. This does not look good on comparison charts when people are deciding which bike to buy. Most road bikes don’t require seals and mountain bikes make up about 10% of the market. Get the picture? Most current bike motors rely on the bearings’ dust seals rather than any dedicated water seal. This situation is good enough for most road bikes but bikes used off road will struggle."
It's certainly opened my eyes a bit and given how popular EMTB's are here in Germany, I wonder how many folk are aware of the potential issues when you use them in their intended way?