the trucking market is so big, I wont be surprised if people would just make aftermarket parts.

If you have 3D printer or CNC machine or injection molding, these parts can be made DYI, to the spec.

for example Tesla charges $1000 to replace a broken passenger side mirror for model Y.

I got aftermarket mirror for $200. I think its a no brainer to use aftermarket part and dont pay 5x markup to the richest man on the planet