prisoners are good because they have no timer...
Check the brigand spawn by Sacrifice moongate, ilshenar - about half the time they will have a prisoner, and half those prisoners will go somewhere with a moongate.
Also, Trinsic's Barrier island is erally good for prisoners - occasionally the brigands will spawn IN the guard zone areas of the island and commit Sosarian suicide-by-cop when they see you by yelling guards as they target you. not only is it a fairly short walk from the island to the moongate, some of the rescues there want to go TO Trinsic, and are deliverable in seconds.