But they are pretty easy and cheap to hook up. The 'tough' part is finding a weatherproof switch (the police switch works nicely for that!). Basically what I did was a fused hot directly from the battery to a standard flasher then to the input on two generic relays (two relays keep the circuit for the left and right separate). Use common wire to switch them, common ground, and run the output from one relay to the hot wire for the left signal, the output from the other relay to the right signal.You can tap the wires easily where they come out of the fairing into the mirror housings. Also a simplier way that someone came up with was just a switch that allowed current to flow from one side to the other. To turn them on, flip the 'new' switch and turn the signals on either side. This assumes they only work with the key on, my way they work with the key off. Hope that gives you some ideas.
