With something like those early model Teslas there is a lot of custom one-off parts that are near impossible to find. The problem is a lot harder.
Auto manufacturers don't design a new pump/bearing/condenser/etc... for every make and model of their vehicles, they take one off of the shelf.
...unless it's a German car. Or so the stories go...
VW has extremely decent availability for spare parts, speaking from experience here. That, and I am not joking here, even extends to sausages - try ordering part # 199 398 500 A ;)
I guess the question becomes why did Tesla have so many one-off parts? Is it all attributable to being electric rather than gas?
Partly yes, but Tesla didn't have a shelf to go grab parts from in the first place, either. They didn't come out of an existing auto company with an existing parts inventory after all. And for the body & frame they also started with a Lotus which is itself not a mass-market car.
You'll probably find _some_ non-custom common parts in a Roadster, like maybe the A/C system. But the drive train makes up a pretty big chunk of the parts in a car.