Buy any old jet ski trailer and move the bunks. The ones with the squares frames are easiest to work on bunk with (mine is really made for a john boat so it's V-shaped).
The harbor freight trailers are around $200. You can buy used trailers for less. If it has good springs and tires, you're in business. Unless, you have the harbor freight trailer sitting arround, you'd be wasting money on it imho.
My trailer was $160, I just put fresh lights on it ($30), took the nice 570 tires off our old harbor freight trailer (awsome trailer, but ours is beat). Once I upgrade the skids, I'll be at about $230 for a pretty nice jet ski traler that's actually made to go into the water.