Volta Supremo can be purchased for 100 uranium once you reach rank 4 and it has an EMP ability. This can be purchased at Juan’s arm dealer. One example - Cortina Weather Station. Map location:
https://imgur.com/a/eaUmymKOnce you see a tank use
to trigger EMP. Then walk up and hijack by clicking
. I found a tank on the road while completing a checkpoint. I don’t have a specific spawn location for a tank, but you should find them pretty often.