Some used car dealers will package a 1-year 3rd party aftermarket warranty with the sale. Depending on the package, the warranty only cover certain car parts, but the engine will definitely be one of them. Every single dealer that I visited during my car hunt last year offered it.

It's so common nowadays, I'd go as far as to say if the dealer decline to include a warranty package, walk away because they could be hiding something that they don't want those warranty providers to find out during pre-sale inspection.