Junk yards are probably most likely place at this point.
Obviously not all step vans but some have them.
I’ve found them on 70’s GM one ton U-Haul trucks.
Other GM 1 tons 60’s through 70’s, possibly 80’s.
No one place to look and find them. Just look for the wheels and don’t worry about what they come off of so long as they are what you need.
