Is it possible to buy a used mail truck (the small ones with right-handed controls) from the U.S. Postal Service?
Yes. The Postal Service has auctions from time to time of used vehicles. Contact a large postal facility near you to find out when they are having auctions. There also used to be a place in Boaz, Alabama that rebuilt old postal jeeps and resold them. I don’t know if they are still in business, but I bought one from them in 1999.