Leaving plants out of the equation just for the sake of the discussion so we don't muddy the waters, it is still practically impossible to get anything today that does not use animal products in some manner. Jebus, even the adhesive used to make plywood uses animal-based glue. Many medications use animal stuff for various reasons. Cosmetics are a given. Organic food is also a given. And the list goes on, and on, and on.
I have nothing at all against vegans or vegetarians. Their body, their choice, none of my business. In fact, I really enjoy some of their dishes a great deal. My only point is that even the most strict vegan is likely not nearly as vegan as they think they are.
Buy the car.
most vegans do the best they can to avoid animal products...for the most part it's entirely impossible to avoid them entirely given how integrated it is into human culture. but doing the best they can in their food, clothing and luxuries while, though unwilling, understanding that they're unable to avoid it 100% doesn't make them any less of a strict vegan...that's just being a realist
but owning a car with all leather interior CAN be avoided and is unnecessary in daily life, thus making it completely understandable that a vegan wouldn't buy it