This is the stuff...
https://www.walmart.com/ip/Stansport...ng-Pad/9856753

We used to get the safety cones from Sports Authority, but they went bankrupt. Additionally, shortly before they closed, we found their supplier changed the plastic formula. They were no longer pliable, they'd shatter. Buggers. Big 5 has cones, but they're too soft. You'd have to at least double them up. Still looking for a good substitute. Hello, Amazon?

But if you can find them, these barriers work. Saved our car's butts many times.