Hot Wheels are cheap as hell and you can buy them everywhere and they last ages. The youngest kid loves them intensely, so of course I'm getting him all the Batmobiles I can.
I obviously started with the car from the 60s series, because that's still the best one ever, but have several from the 90s films, and the one from the much-missed Brave and Bold cartoon. I need to get one from the most recent movie, because that was a terrific car, even if it has to have some kind of nuclear or jet propulsion to really be a proper Batmobile.
They're all very sleek and very sturdy, and are getting much attention from the young one. And the best part is find them lying around the house - buried in brown sugar or in the sock drawer. I don't know what they're doing there, not even Batman could figure that out, but it's damn near the most fun you can have with a Batmobile without ever actually getting in one.