Get a cattle or horse fence electric power supply. Some $50.
Drag a ground strap, insulated from chassis, along ground. Connect this to the ground side of the power unit. Connect the hot side to the chassis.
Have a way to turn off so you don’t get zapped when you get out.
Maybe you can find a 12v powered one online. Mine is 120v, so use an inverter in the car.
I have this to protect my chicken from coyotes.
https://www.speedritechargers.com/products/patriot-pe-10-110v-ac-powered-fence-charger-10-mile-40-acre-free-shipping-and-fence-tester?variant=22257904091194&gclid=EAIaIQobChMIs-D8-cPe6QIV1MDICh3YEgtNEAQYCyABEgITFfD_BwE
Drag a braid type electrical strap.