I just used the Pirate Search tool with minimum level set to 5 below my current level and max set to 1 below it, the minimum money was left blank and the selector for attackable was on Yes. I got a list of about four one of whom was carrying money. When I tried to mug them I was told they were too low a level, I tried again with an attack and got a similar message.
Going back to the search I tried with values of 1 - 35 & Yes and saw swarms including some at level 4, repeating the search with attackable set to No yielded no names at all.