The brake wear sensor on the front left side came loose. Possibly a chunk of tire I hit on a recent trip. The dangling sensor then cut through the outer driveshaft boot. Mini does not sell boots. $1000 for a complete driveshaft. Maybe I can find a boot, maybe I can't. This is not the first brake sensor I've had come loose on a car. I will be bypassing it once I've dealt with the boot. Rotors are way cheaper and easier to replace than driveshaft boots...
There are universal CV joint boots + glue available but if the area is small enough you could get away with the inner bike tube patch kit method.