One option is to get bar-end turn-signals. The wider angle allows them to be seen better by following vehicles. Though you do have a potential to block view depending on what you are wearing, how wide you are, etc. You could also add some fender mounted ones that mount flush against the fender. There are some tail-brake-lights that have integrated turn signals but they are really a bad ideas -- not enough angular separation for following vehicle to tell which way you are signaling.