In addition to the retreat listings on this website, there are other ways of finding retreats for pastors.
You may be surprised how many folks will come through if you just let your needs be known. Even in the impoverished inner-city neighborhood where I pastor, there are families which own a share in family vacation homes that have been passed down for generations.
Many Christian campgrounds offer free or discounted lodging for pastors, especially if they share a denominational affiliation. Don't be shy about asking.
Many monasteries, convents, and other Catholic retreat centers offer modest-priced accommodations open to both Catholics and non-Catholics.
Many organizations - like denominational bodies, campgrounds, and counseling centers organize group retreats. These are usually different from the retreats this site concentrates on. They are generally larger group events, and often have more of an educational or missional focus than a rest or renewal focus.