If you have decent credit, you might be able to just use your existing vehicle and small amount of cash as a down payment on a used vehicle at a regular car dealership. For a used car dealership specifically, I heard J&M in naugatuck has good quality used cars, although I never bought from them myself.

If you have bad credit and little cash for a down payment, you'll probably be stuck going to a "buy here pay here" used dealership, of which there are many all over. They help people with bad credit get a vehicle, but charge much more than it is worth because they no these people have no other option. Those dealerships sometimes put a device in the car that prevents you from starting it if you are behind on the payments.