You are thinking in postwar era in terms of parts - if you want that tree today you have to buy the car - it is not just Lionel - it is how businesses have to manage costs now
Hunt for the car used on eBay and Trainz and such
Option 2 - you can get trees and make your own with 3mm led kits and a power/driver circuit to connect to a roller pick-up truck (Lionel does keep those in stock)